And last: this may be short lived and resolve on its own. Or not. But learning to tolerate some discomfort is a helpful skill to have.

There is always more math! Find out what they are working on and do your own tutoring at home for next level math concepts. Ask if you can send worksheets from home.

You could ask the teacher what would be approved to send in. For example, one of my kids always had a book in her bag she could read when she finished work before others

Somewhat echoing your take already, not everything in life needs to be optimized. Parenting lesson I wish I learned earlier...

A few thoughts, in no particular order. One angle you could take is (depending on the level of anger) take the opportunity to use this to work on emotion regulation strategies. Boredom isn't necessarily a bad thing! It is an opportunity to do so many alternative things that would be kid directed.

Yeah, that tracks

Dude, go watch last week tonight rn

better because... wood? Not seeing it