on books in classrooms

This morning, reviewing notes I’ve stashed away (and realizing how important it is that I wrote things down), I came across this:

In one day, I visited three different 8th grade classrooms, and in each of those classes they used their textbooks:

In the first, they used them to prop up inclined planes.

In another, they used them as masses that were being dragged by a force scale.

In the third, they used them on the input end of a lever arm to lift up a student.

The books were never opened.