The student teaching experience is a real mixed bag. If you are lucky, your supervising teacher will be a real mentor, who not only passes on skills, but gives you insights into the crucial social and political factors in your school building that can impact on your ability to be a good teacher.
If you are unlucky, it is a different story. You can tell if you’re one of the misfortunate ones if your supervising teacher disappears after your first meeting. That teacher will tell you something along the lines that the best way to approach teaching is by the “sink or swim method” which you can only “work out for yourself.”
Actually, the sink or swim approach is good for people who already have the skills and enough strength of character to deal with a classroom full of kids. Few do.
Student teaching, like mentoring, are two ideas which sound good in theory. However, in practice they are easily subverted into something else. Student teaching becomes, for example, free time for the "supervising" teachers. Mentoring becomes ingratiating oneself with the principal who “needed” to find “someone” to take on student teachers.
Principals often take as many student teachers as they can get because they themselves are taking courses for the superintendency and the student teachers come out of the same department the administrator’s professors are in. Getting student teachers placed has higher priority than making a good student-mentor match.
To examine these issues further, see Mentoring: Are We Serious?