A. Let's get a grip here. First of all, it's the beginning of the school year. Teachers and preschoolers are still getting comfortable with one another. Your active child and Ms. Mild-Mannered could work it out, and you should let them try to do so.
Student-teacher chemistry is kind of a crapshoot, and you can't rescue your child from every teacher he clashes with. Besides, teachers are only humans doing a tough job.
You also need to cast as honest an eye on your child as you do on his teacher, and at least consider whether the solution has more to do with taming your son's behavior than with changing his teacher's personality. Taming behavior doesn't mean crushing a child's self-esteem. It means letting him know it's not fine to act like a maniac everywhere or all the time. At home, unconditional love and acceptance may be a given. At school, as in life, there are conditions.
Bear in mind, too, that the teacher knows your child out of context. You might make an effort to give her some by volunteering once in a while to come into the classroom, or just chatting with her at pickup or dropoff.
Mrs. Gundersheim, Madeline's 30-year-veteran kindergarten teacher, admitted to me at the end of the school year that initially she thought our willful girl was a "spoiled brat." But as she got to know her and us better, Mrs. G. said that she realized our little sweetie-pie wasn't spoiled, just a major piece of work -- an assessment we had to agree with.