If it were true that you just received a(n) email from a teacher with that many errors, and assuming you have the ability to count and correct each one, then you'd be able to provide a specific number instead of an ambiguous range, along with examples of the most egregious mistakes. SYH won't help with this fairy tale, but I can.

"Teacher" is singular, "them" and "their" are plural. You flunked.