Here are a few suggestions:
1. It sounds like there is some kind of error in the server settings for your IMAP account. It might be a good idea for you to contact someone in your school's tech department or consult their website to verify you have the correct settings.
2. Activesync will indeed synchronize all of the information you listed with Outlook. If you are worried about losing contacts from your phone, I highly recommend using either
dashwire or
pimbackup.
I hope this helps.