This looks like an XY problem[0] on a massive scale.
Because the grown-ups can't figure out how to solve the top-level problems, they are instead dealing with the low-level symptoms and applying band-aids.
It also reeks of political pork to me.
I admit that enumerating the top-level problems is politically fraught, but I think they can be neatly condensed into:
* that mass shootings occur, ever
* that we cannot control childrens' use of the internet in any meaningful way
* that children are seeing through the thin veneer of meaningfulness that life in the US is supposed to have (notably traditional career paths and religion)
I don't pretend to have easy answers, but see-through backpacks is security theater that is the stuff of Bruce Schneier competitions.