Mailing Issues
Administrators - they have the job of sorting your mail so ignore them at your peril.
Envelopes - do different sizes and types make any difference?
Mailmerge - does it help to mailmerge in the name and address of the teacher into the letter?
Follow-up - does it help to follow up with a phone call or another mailing?
Mailing out - when it is best to use a mailing house.