I've always found that in creating a tag taxonomy, perfect is the enemy of good — there are a lot of factors which are useful for the question, and that could group questions, but we don't need every bit of information to go in the tags

So that's why I've suggested just focusing on broad ranges and course tags (and the course tags by proxy imply age in some ways... generally, most people taking a qualification in school do it at the same age, but this rigidity does break down outside that environment)

@Aurora0001 You have good instincts.

Slow day on the site, but a busy day for me.

(I've noticed a correlatory relationship between those)