A Smaller Class Makes a Huge Difference

I occasionally reference Staples High School's large class sizes, so I thought I'd break down some of the math of how relatively small differences in class size turn into relatively large differences for individual kids. With section sizes frequently approaching 30 students, I'm not sure everybody realizes what a big difference it is when you can make sections even slightly smaller.

When it comes to giving feedback on student writing, one of the most fundamental parts of teaching kids how to write like college students or professional adults, it's shocking what a small difference in section size ends up meaning for a kid.

Say I have 120 hours of time a quarter (about 12 hours a week) to devote to giving individualized feedback on kids' written work. If I have 29 kids in all 4 sections, that's 464 drafts of papers (2 papers with 2 drafts each per kid) I have to grade. That gives me 15 minutes per draft. It would be nigh-impossible to find much more time than that, so the kids probably won't get any more than that bare minimum. In reality, many drafts take longer than that, and we probably devote more than 12 hours a week to individual feedback, but you get the idea.

Let's do the same math with class sizes of 22. That's 352 drafts a quarter. At 15 minutes each, that's roughly 90 hours of work. That leaves me 30 of my grading hours to divide among my kids. That means I can devote over 20 minutes per kid per quarter to additional feedback. That could mean a whole other paper, or another draft of a revised paper. It could mean time for an alternative assignment, like a presentation. If I devote it to an additional paper, that means that a kid gets something like a 30% increase in direct feedback on writing and a greater-than-30% increase in the amount of writing assigned.

In the classroom, an oversized section cuts the individual attention and time each kid gets. In a 19th-century model, that doesn't seem so bad. Who cares how many kids are listening if the teacher is just lecturing and making them copy notes off the board? As long as he can keep control of the room, it doesn't really matter if he's got 22 or 29 kids. I think a lot of people who don't find the class size issue so urgent are suffering under the misconception that good teaching is done with the teacher in front of the room and the students in orderly rows, copying down facts.

In an excellent 21st-century classroom, however, kids are rarely just copying things down. They're discussing, researching, problem-solving, owning their own ideas, presenting concepts, receiving feedback, working individually, or working together, all dependent on whatever model is best for the given material.

Small shifts in class size result in dramatic shifts in the education a student can receive. In a 50 minute class with 29 kids, there's time to give each kid 103 seconds of individualized attention, whether that means a chance to speak his or her mind in discussion or time with the teacher looking over his or her shoulder, giving pointers on individual or group work. In a class of 22, that's 136 seconds each. Over the year (145 class sessions), that's 80 more minutes of individualized instruction a kid gets in a class of 22 versus a class of 29. In the smaller class, each kid gets over 1/3 more time to test out ideas, practice presentation skills, gain confidence, and get direct teacher support.

There's also a significant diseconomy of scale in a larger class. Tasks like handing books out or getting a class's attention take disproportionately longer with each kid you add. That procedural diseconomy takes minutes away from real instruction and individual attention. So in the larger class, the kid gets smaller proportion of a pie that's smaller in the first place.

Those feedback and class time numbers obviously don't take into account many of the vagaries of real-world teaching, but the ratios are roughly accurate when it comes to the amount of individual instruction and feedback a student gets. If we taught only lecture-based courses, class size would have little impact, but world-class educators don't teach with that assembly-line mentality because we aren't trying to create assembly line workers. A world-class education demands that we keep class sizes down, and even the most meager reductions in class size pay off disproportionately in the education our kids get.

To put it very simply, reducing class size by 25% results in at least a 30% increase in the support and individual attention a student gets, both in and out of the classroom. We have to fight to keep class sizes as small as we possibly can if we want to lay claim to meaningful leadership in education.