We got more input by attending a staff meeting and just sending a letter asking for their input. We have a PTO mailbox in the main office and we encouraged them to give us their ideas and feedback. Since we followed through on so many of then and gave the teacher the credit, we have a great response rate each year.
If its a formal as a survey, they may not respond.

Hi
I was wondering if anybody would share with me a teacher survey you put out? This is my first year as PTO president and I have put out a survey for parents and received a good response. I want to include the teachers too to hear their ideas/gripes.
Thanks
Deb