I went through this a few years back and didn't care for the custom MMC approach. For the life of me I can't remember why though... Anyways, I wound up writing a VB app that lets teachers unlock and reset passwords for student accounts. It's been through a couple revisions and one total rewrite as it was written in VB6 in its first version, and then VB .Net 2010. It gives staff a breakdown by grad year in a treeview and allows partial searches for student names and ID numbers. It'll even show student pictures if they have one.
The rights to change the lockout and password attributes on the student's accounts must be granted on whatever OU students accounts reside in.
Don't be afraid to download VB .Net 2010 Express and give it a try. It was actually a lot of fun learning how to put this together.