Is there any way to recover an old school email account?

You might want to consider how long ago you left school. Many institutions will wipe accounts after a few weeks or months of inactivity. If that's the case, then those emails and documents likely can’t be restored. It's a tough situation, so if you can, try to get confirmation from the school on the status of the email.

Unfortunately, the best solution usually comes from the school itself. If they say nothing can be done, it might be that the account is permanently deleted. Most schools have a policy where they delete student accounts after a certain period. Once it's deleted, it’s often not recoverable, so you might just need to accept that it's gone.

I understand your frustration, but I wouldn't recommend any hacking attempts. It sounds like that account was tied to your time at school, and accessing it after leaving can get complicated. If those documents were so important, it might have been a good idea to back them up elsewhere.