If you've spent any time engaged in instructional design or learning engineering-if you've consulted with educator as s they work to build or improve instruction-you've asked an educator some variant of "Why are you teaching this?" or "Do students really need to know this?" 1/x

I've asked these questions A LOT. I've watched my colleagues ask these questions, over and over again. What's most important? What MUST your students be able to do? What MUST they know? 2/x

Which is why today's work on Big O notation and quadratic growth is just embarrassing. In my Intro to CS for non majors, I inherited a fantastic set of slides, including a nice unpacking of the math involved in determining Big O for insertion sort (n^2 if you didn't know) 3/x

But every year, I find that despite these great slides, my students struggle to understand how we move from the counting of iterations and operations to getting to n^2. So every year I expand this section...more details and a slower pace on how (n-1)*n/2 4/x

becomes (n-1) * 2n + (n-1)*n/2 which eventually becomes n^2. Which becomes O(n^2). And so every year I try to break it down into smaller, easier to understand pieces. More slides. More explanation. More lovely diagrams. 5/x

Our covid-inspired move to online is demanding a more thoughtful use of synchronous time, and I've been working hard to throw overboard all the stuff that's non essential this summer. This is hard. It's harder than you'd think given the way I advise other educators. 6/x

So, I realized in prepping our next class meeting that as I've worked to provide more bite-sized steps on the move to quadratic growth, the math explanation has grown...and grown. 34 of my 74 slides on this topic are now devoted to UNPACKING THE MATH. 7/x

I'm teaching intro for non-majors -- I don't expect my students to do these mathematics. I don't assess them on it. Some fraction of my students are in domains that this section puts them to sleep. The rest are seeing this detail and are terrified. And confused. 8/x

So: I don't care if my students can do this. I don't expect my students to do this. Why am I spending more than 50% of the meeting (and a lot of time and sweat on better slides) trying to teach it? This is bonkers. 9/x

How we teach...how we engage as educators is so deeply personal. And some days it may simply reflect all the neurosis we carry as educators. And this is a case study; I'd have never let an OLI course author I was advising get caught up in this. Awake at the podium...10/x

...asleep at the switch -- the struggle is real. But I'm also not sure that-outside of COVID forcing me to maximize and consider every synchronous minute I have with students-I'd have caught this (egregious!) example issue of wasted time. 11/x

Anyway, lessons from this form me: tomorrow, I'm tossing half my slide deck. Terrifying. Also: The act of interrogating and improving our instruction is never done. We'll see tomorrow if I can do better with less. 12/12