Currently being a student teacher myself and just finishing my first placement in a lower level grade, I can give you insight on what student teachers want in a mentor teacher!

I am sure the student teachers university or college will give you specific details on what the student teacher must complete while in your classroom.
I really liked to mentor teacher I was assigned. However, we have VERY different teaching styles. So, I think you should have an open mind. Let your student teacher try new things, even if you would not do them the same way. Be prepared to answer lots of questions (as student teachers we are curious and still learning)! Give advice but let your student teacher figure out things for her or himself on occasion. Most of all undestand that your student teacher isn't going to do everything perfect! We are still learning and make lots of mistakes!
