if you are getting to your box to get the error then the school isn't blocking out bound 22 which is good.
You can check you logs in /var/log as root
interesting ones are messages, secure and xferlog
command
Code:
tail -f messages  # this Keeps the logs continuous ctl-c gets you out
tail -100 messages  #this gives you the last 100 messages and so forth
same code works for secure and xferlog
messages are system logs
secure is breakin and security logs # this is most likes where you will get your IP from your school
xferlog is a log of ftp transfers. This is where you for sure find out if you have been hacked if files moved and you haven't done it.

usually xferlog is empty.
Let me know if this helps or if you need more clarification.
Mike