What is a guidance secretary?

My guess is that you are referring to a secretary who works in the guidance department of a high school or middle school. These secretaries help guidance counselors organize their calendars, usually have some responsibility over student records, and may be called upon to copy and mail records and college applications for students at the school. They will also do any number of other things that will demonstrate, as usual, that secretaries are the heart of almost any staff and are the individuals that end up making everything work.