Vlorbik on Math Ed

KTM regular Barry Garelick recently published a three part series on (what so-called “reformers” insist on calling) “traditional” methods in elementary mathematics education. The fight-the-reader page design isn’t his fault.
Better Explained gets enthusiastic about Pythagoras.
Eugenia Cheng (and Aaron Lauda)’s guidebook on Higher-Dimensional Categories appears to be something I’ll want to look at. Good thing I’ve just bookmarked it. (I spotted her in this thread at the ever-fascinating Gowers’s.)
Reasonable Deviations briefly reviews a paper on infinitesmals.