Thursday, July 31, 2014

Thinking About Calculus

If you teach Calculus in high school, you probably have a similar observation as mine that the student population is highly heterogeneous (a fact that is perhaps surprising to outsiders). Many students feel pressure from their parents and peers (ie. social pressure) to stay on the Calculus track, so within the same group they can span truly a wide range, from those who really could have benefited from another year of Precalculus-type skills-building, to those who are somewhat okay with procedures but who really need more experience/exposure with integrated problem-solving (something like a "Math 4" course that involves college-level math language), to those who are truly ready -- and eager -- to tackle new topics, both conceptually and algebraically.

I stumbled across this research summary from years ago (dated 1988) that noted a shift in college Calculus curricula away from conceptual understanding and toward procedural manipulation. Even though the article is dated, I find myself torn in the middle of a similar tug-of-war in my own thinking of Calculus. Fortunately, I teach a non-AP class, but my juniors (within a class mixed with seniors) do largely feed into another year of Multivariable Calculus after my class (combined with students from another class), so I have to take that into consideration in organizing my course. But, the statement from the article that we're trying to make the course "be all things to all people" really resonates with me. In the same class, I am supposed (and trying!) to differentiate so much as to help all the kids who need an extra year of algebra practice; to help all the kids who need an extra year of problem-solving; to cover all the major Calculus concepts; and to develop all of their skills as learners and to nurture their mathematical practices (all of which, mind you, take time). It was really half a miracle that many of the kids ended up enjoying and appreciating the experience of my first year of trial-by-fire to accomplish ALL of this at a new school; the task set for us can be daunting, frustrating, or exciting, depending on how you choose to look at it. 

One of the things that I did this year which actually helped a lot with teaching a heterogeneous group was to make sure that I made time for projects in this class. The projects gave the kids time to self-differentiate. Many of the kids kept working on their projects until the last minute, throwing in extra features or sometimes even working on it after it was due and presented. The next year, I will keep most of the projects but re-arrange the pacing so that they are better timed and hopefully a little less stressful for the kids. 

Projects I did:
* Economics mini-project (but this one I will switch out for something better, more individualized)
* Graphical organizer showing connections between all the learned skills
* Rollercoaster design using piecewise functions
* Function pictures including shaded definite integrals (calculated via GeoGebra but also by hand)
* 3D-modeling using vases that they created and volumes of revolution / scaling up to find and test against real volumes

I also did a group quiz this year on the minimization of coordinate distances (to help review the distance formula) and on related rates, which was assigned to be completed mostly outside of class. It was such a great experience for me and most of the kids, that I'll definitely have to find some opportunity to repeat it. I decided that next year, I'll have to bump up the Function Pictures project to the first grading period, to help the kids review functional forms and inverses. That way, when we revisit their projects to fill in the integrals later on in the year, their focus will be more on the integrals and less on the outlines.

Since I need to replace the economics mini-project, I am going to try doing a sustainability project this year, that involves some regression and rate-analysis at the start of the year, and then have an individual component where the kids look for something else (an interesting data set) that does not have a time domain, to extend their understanding of rates beyond the time domain.

Another choice that really helped me with approaching the heterogeneity was teaching Calculus in reverse. First, we did a lot of graph sketching and graphical analysis by calculator. This evened out the playing field because the kids who were weak with prerequisite algebra skills could still access and feel successful immediately about the new concepts. Then, we learned differential Calculus skills via exploration, which helped the kids build some of those valuable mathematical practices and to build their confidence in playing around with math. I took our time on this part of the course, to go through old algebra skills and to practice things that were challenging as they came up. The really intuitive students started during this unit to peek ahead on their own at how to procedurally un-do differentiation. After the derivative skills, I took a significant amount of time to work on related rates with the kids, to give everyone some quality time with problem-solving. (It wasn't nearly enough time though. Obviously, you can never spend enough time on teaching and practicing problem-solving.) Later, through explorations, the students were able to gather most of the core concepts about integrals. We then used projects to reinforce their algebra skills. Limits came last in my course (because it is the most abstract, and I think it made the most sense to introduce it last as a way to prove the things we thought were true), and at that point, it was a really nice tie-up of the whole year, reinforcing the definitions we had learned throughout the year regarding derivatives and anti-derivatives by proving them via limits.

Even though I have been thoughtful with my course, I wish I could feel more certain that I am making the right choices for my class. For everything that I decided to spend more time on, it was a choice to leave something out. I tried to keep the class fluid, so that if an interesting question came up during a project with a bunch of kids, I expanded that during the next class to go into the relevant material, even if it's not part of the classic Calculus 1 curriculum. (For example, my students really wanted to know how to integrate circular areas on their projects, so we did an example together and about a third of the class then followed suit to use trig-substitution to help them on their projects.) Never in my class did I feel like I had wasted time, but I couldn't shake the feeling that Calculus 1, the way that I was teaching the class, could easily have spanned 1.5 years.

What do you think? What choices have you had to make for your own Calculus classes? Do you think they are worth it?

1 comment:

  1. Hi Mimi. I never think there's enough time to do everything, and always second guess what I include or leave out. Then I make myself feel better by thinking that it's not WHAT I teach that's the most important, it's the "thinking" and "exploring" and the "how to take risks" and "how to process" and "how to persevere" skills that will stick with the kids in the end. Most topics, I think they'll forget the details in a year or two if they don't revisit them. So, don't know if I'm rationalizing things away, but there it is.