Frustration in trying to use Khan Academy exercises

The teacher reporting tools just don’t work.  So it’s taking me FOREVER to check students’ progress.  Literally, there are exercises on their site, which I have assigned to students, that are not in their list of exercises in the teacher reporting tools.  To check student progress, I have to go to each student, click on their name, and CONTROL + F to search the page for the name of the exercise, then look at their score, and finally type it into my gradebook.  And, because student proficiency changes constantly based on the mini retention quizzes KA gives (called mastery challenges), I will have to re-check student scores on each exercise every couple weeks.  KA, you say Shipping Beats Perfection doesn’t mean you ship things that are broken, but this is clearly broken!

UPDATE: Khan Academy Lead Developer Ben Kamens comments on this bug and on their current focus in building out more teacher reporting tools.  See comments section.

UPDATE: I found a new workaround, and I’m pretty sure it wasn’t there yesterday.  Perhaps KA fixed something already.  You can use CTRL + F to search the table when you view by table.  Exercises that weren’t in the table yesterday seem to be there today.  You can’t type their names into the search box above the table, but you can use your browser’s search function.  That’s a start.

UPDATE 9/22/13: Now that searching in the grid is working, what’s not working is searching in a student’s skill progress while viewing their profile.  So, for example, when a student has completed “Multiplying Expressions 0.5”, I can see their work in the grid or in the coach report by student, but if we view the student’s “skill progress” from his/her own profile, Multiplying Expressions 0.5 is not listed as an exercise.  In essence, KA’s back-end system for tracking performance seems to be having a hard time keeping up with its front end improvements this summer. so teachers should be prepared to potentially spend extra time figuring things out.

UPDATE 9/29/13: The issues with the teacher reporting have been completely fixed, and–even better–they have added a feature which lets you recommend exercises to students as a whole group rather than one student at a time.  Nice job, KA.  Exactly what I was hoping for.

How I’m Covering the Distributive Property in Precalc

I teach a class called Math Analysis/Trigonometry, which is close enough to Precalc that students who get A’s in my class are allowed to skip to calc. I’m spending the first several class periods covering a combination of Carol Dweck mindset stuff and the idea of distributing.  Distributing?  In Math Analysis/Trigonometry?  Yes.  I actually think many students, even post-Algebra 2, don’t understand it that well, and I think it’s what leads them to make some of their most common mistakes.


Later in this post, I’ll describe how I’m trying to talk about distribution in a way that’s conceptual and allows for Accountable Talk–I certainly don’t want to lead off the year with a bunch of drill-and-kill.  And to my surprise, distribution seems to be fertile ground for conjecture and discussion.  But first, here are the top 2 mistakes.  Recognize them?

  1. In (x + 2)/x , you can cancel out the x’s.
  2. (x + 5)2 is just x2 + 25

With mistake #1, students just don’t see that it’s distribution.  If it said x(x+2), they wouldn’t give the answer of x2 + 2, but they don’t see that distribution happens with division, too.  Somewhere in their brains, they know it, but that knowledge must be only loosely connected to everything else.

With mistake #2, students mistakenly think that you can “distribute” an exponent across addition.

There are other big mistakes relating to distribution, too.  Have you ever seen someone try to distribute the 2 in 2(3 * x)?  Usually, they won’t do it for 2(3x), but if I put a multiplication sign and some big spaces inside the parentheses, I usually get more than a handful who distribute.  This whole topic is closely connected to the ability to see whether an expression has one term or many, but the number-of-terms idea doesn’t unify it completely, because you can “distribute” the square in (3x)2, even though 3x is a single term.  So let me share what I’ve done.  Curious how you would have done it–surely other teachers must have to do battle with the same misconceptions.  And you may object to the use of the term “distributing” when talking about an exponent.  I used to discourage students from talking about it like that, but I now think allowing it as long as they have a deep understanding of distribution is better.

Accountable Talk Discussion Plan

Discussion was grounded in this student handout. The question of why the distributive property works led to some crickets chirping in class, so I had to take a student’s example from #1 — the example was 3(x + 2) — and ask WHY does it equal 3x + 6.  The first 3 students to respond gave variations on the theme that you have to multiply the 3 by both terms inside.  Right, but WHY is that rule correct?  I think I ended up priming the pump by writing “3x = x + x + x” and asking how you could write a similar statement for 3(x + 2).  A student explained that (x + 2) + (x + 2) + (x + 2) = 3x + 6.  Still, lots of students were either tuning out (“Isn’t it obvious that it’s 3x + 6?  I mean, you just distribute.”  Grrr) or not getting it.  After 3 more students paraphrased and small groups checked in with each of their members, everyone seemed to understand the point we were making.

So then, the set-up for the big discussion: #3 on the handout.  To clarify the question, I said, “There are other situations where you can distribute.  For example, what could you put inside the parentheses in the expression (     )2 so that you could distribute the square.  And 90-100% of the class wrote something like (x + y)2.  Success!  This was exactly the misconception I wanted to address, and instead of just presenting it from out of nowhere, we’ve created a natural context in which to debate it.  I grabbed a bunch of student responses and put them under the document camera.  One student actually wrote out his work: (x + 5)2 = x2 + 52 = x2 + 25,  I showed that response last, and a handful of students recognized that it was incorrect, but the bell was about to ring.

Bell rings, end of class, next class begins.  We picked apart what was wrong with (x + 5)2 = x2 + 25, and I asked them to try #3 again.  What can you put in the parentheses so you can distribute the square in (     )2.  Now a couple of students tried a monomial in the parentheses.  We proved that it worked using associativity and commutativity, and I asked several students to summarize.  So far, the class thinks the rule is that you can distribute an exponent across different things as long as there’s no addition or subtraction between those things.  That’s not the rule I want them to eventually come up with, but it’s a good enough start to let us move on to #4.

Check out #4 on the handout (here it is again).  I really hope we get some good mistakes there, and some good debate.  The rule I want them to generalize is that you can distribute what’s outside the parentheses if the operation/function outside is the repeated version of the operation inside.  Since raising to a power is repeated multiplication, an exponent distributes across multiplication but not addition.  Since multiplication is repeated addition, it distributes across addition (or subtraction) but nothing else.

Actually, I’m not sure if this is technically correct.  Distribution is a property of rings from abstract algebra, and there may be some exotic versions of rings where the “multiplication” operation doesn’t represent repeating the “addition” operation.  I got some help on Twitter from Dave Radcliffe (@daveinstpaul), who was telling me about power sets forming a commutative ring.  If anyone can help me understand whether I’m making a big mistake talking about distribution this way, I’d really appreciate it!

Khan Academy for Review Practice?

Meanwhile, my students have a bunch of factoring and quadratics exercises to do on Khan Academy.  (Yes, on Khan Academy.  These kids won’t be harmed by boring videos about factoring.  They learned factoring years ago.  They just need to gain fluency, and I need data on who needs remediation with what.)

UPDATE 9/11/13: When we did #4a today, students’ initial answers on whether to distribute in 2(3 * x) were evenly split.  Half the students got 12x, and half the students got 6x, until we discussed it.  Should get to the final summarization of the principle I’m looking for tomorrow.  (We don’t spend all class on this stuff, so it’s getting spread out over more days).

How I want to teach horizontal function transformations

Horizontal function transformations are tough to teach.  Sure, you can just tell students how they work (“everything is backwards inside the parentheses, so minus makes you go to the right”), but that just seems arbitrary and pointless to students.  Slightly better would be to let students discover by a process of induction that directionality is reversed inside the parentheses, and then get into the big discussion of Why?  My sense is that this is Dan Meyer’s preferred approach, based on his comment in this post by Kate Nowak, who is struggling with teaching this concept in the quadratic function family.  And I have nothing against Dan’s approach–letting the induction come first is fine, but it’s really the Why? that’s tough about this idea.

First of all, it’s not just the directionality that’s reversed–it’s also the order of operations.  So in sin(2x + pi), everything is shifted left by pi first, and then contracted by a factor of 1/2.  The “+ pi” is dealt with before the “2*”.  How are students supposed to discover that fact by induction, and even if they do discover it, how will that set them up to make meaning out of it?  I am not a fan of induction just for the sake of having students discover things when that discovery does not build connections or make meaning.  I mean, you could theoretically have students “discover” the rules for integer operations by letting them play around with a calculator and look for patterns, but that would still be an awfully shallow learning experience.

To return to the question of horizontal transformations, here’s an idea I’ve been cooking for a few years: teach the concept in the context of encryption.  We all know the idea of encoding by letting 1=A, 2=B, etc.  But as Julius Caesar found, it’s better to introduce a shift into your code, e.g., 1=Y, 2=Z, 3=A, 4=B, …  This shift works in the same way as a horizontal translation.  Pow!  A real-world, intuitive example (I hope) of an otherwise difficult concept.  The example even generalizes pretty easily to show why order of operations is backwards as well.  Here’s how I’d use this hook in class:

  • First, give students an encoded version of a sentence (with no shift applied), and ask them what they think it says.  I’d say something like, “Ender’s Game is Better than the Hunger Games”.  So “Ender’s” would be encoded as “5  14  4  5  18 ‘ 19”  Shouldn’t take long before someone cracks the code.
  • Then discuss why a shift would be nice–both you and the message recipient would have to agree on the shift in advance, but it would be more secure.  Maybe I’d show the video linked above about Caesar and his cipher.
  • The class would agree on a small shift, say -3.  Now, to read a message, you subtract 3 from each number, and then decode.
  • I’d ask each student to write a message and encode it so it can be decoded with a shift of -3.  They’d check their work by decoding their own message before exchanging with other people and decoding each others’.
  • Here’s the point: to encode when the shift is -3, you have to start by adding 3 to each number, since the recipient will then subtract 3.  So far, this should all be fun–little complaining about “when are we ever going to use this.”
  • Then I can introduce a graphical representation of the code.  It might look something like this:













That’s the graph of the original code.  I’d ask students for the graph of the new code, with the shift.  The shape would be shifted to the right by 3.

  • Of course, this concept would work with any original code–it wouldn’t have to be 1=A, 2=B,… to start.  It could be 1=Z, 2=Y, … or any one-to-one function to start.  This lets us talk about functions versus relations in an intuitive and meaningful way in the same lesson.
  • I developed the connection to inverse order of operations a little bit in my first attempt at this lesson last year.  Here it is on dropbox.  It was a success in the sense that students finally understood that between reversing direction and order of operations with horizontal transformations is just an application of “undoing” an expression to solve an equation.  But I thought the lesson design and delivery were a little clunky.  I plan to revise it for future use.  But if someone else likes the idea and revises it first, and then shares it with the rest of us, well, I won’t object…

That’s it!  So, what do you think?

UPDATE: the formatting seems all messed up in my dropbox .docx link, so here’s a pdf version

FURTHER UPDATE: Oops, in my original post, I had the grid showing the “graph” of the original code transposed.  That is now fixed.

From the comments:

Dan Meyer: Great to see you blogging on the regular, Kevin. We seem to be on the same page here that discovery without building connections between the discoveries and axioms is kind of useless. But using a real-world context here seems risky also. Is it possible that the cryptography connection will obscures mathematical meaning? How do you help students make the leap from Caesar Augustus to periods and amplitudes?

(My response to Dan’s question is in the comments below).

Hey education researchers! Here’s how to get teachers involved.

I have an idea for how education researchers and teachers could connect better in order to really see what principles that researchers are positing really translate robustly to the classroom. The short version is that students or researchers who want to study a learning principle could embed their experiment in one of the lessons from Dan’s summer “Makeover Mondays” series, in which Dan remakes boring problems/tasks from textbooks into more inspiring lessons.

These makeovers often raise theoretical questions for me, such as how much to ask students to discover for themselves, and when to schedule the “drill practice” (e.g., in bits and pieces during an investigation, or after it?). A good example would be the task called Shipping Routes, in which students apply/discover least common multiples to predict the first time two ferries with different round-trip times will be in phase with each other. Dan’s makeover involves sending students to this simulator to look for patterns in the scenario.

Testing learning principles in the context of these lessons seems to offer a few advantages:

  • If learning sciences researchers want to connect with the teacher community, they have to connect either before or after they do a study. Connecting afterwards means doing the study first, and then trying to get teachers interested in it. This has all sorts of pitfalls. You have to describe the debate your study informs, and people can accuse you of mischaracterizing their position or get sucked down a black whole of semantic arguments. You have to describe whether you think the results are broadly or narrowly applicable, but that part may not be heard. Etc.
  • Connecting before means getting teachers interested in the study before doing it. With this approach, you don’t have to worry as much about recreating the debate before situating your results in it. You can just describe your experiment and empirical results, and the discussion community will do that framing for you and translating from theory into practice for you. That’s what I’m suggesting here.
  • Many of the redesigned lessons often involve some kind of software interaction that could be used to log student behavior. And the lessons are commercial-quality, but you don’t have copyright issues because they’re usually licensed Creative Commons.
  • The final products of the lessons bubble up through Twitter, blogs, etc. from a community teachers. All of those teachers would be very interested in reading an article about a lesson they’ve tweeted about and given serious thought to (or plan to teach!).
  • Dan’s blog is read and commented on by opinion leaders among math teachers, such as Grant Wiggins (the co-creater of Understanding by Design) and Michael Serra (author of the Discovering Geometry textbook series that’s very popular). So it’s a robust conversation.

So what do you think, MTBoS? Is this a good idea?