Please consider homeschooling if you think it's something you or someone in your family could do. At least for a year or so. Don't put your child in a school that has labeled him before he even stepped through the door. He may have ADHD and many, many parents homeschool kids with these types of problems with success. And he may not have it.
My sister (15 at the time) went in last year to get tested for a reading problem. She was sent to a doctor by her pediatrician. She walked in the room, not five mins later the guy said she was ADHD and suggested medication. It was so appalling and my sister who is almost 17 now, has had to deal with a reading comprehension problem on her own.
Some schools and some doctors get kick backs from the drug companies. Please keep that in mind before you load your children up.
They want your naturally active little boy to be drugged. They see him as a problem because he can't sit still. 20 + years ago when you and I went to K, we got to color (outside the lines), learn to cut, sing, and play. Now it's Spanish, sitting in desks without moving for several hours, computers, math, reading, and writing. Some kids just don't fit in that environment.
I have worked in daycares, preschools, and elem schools in several states for years before my daughter was born. My mom worked at a high end preschool in Miami for several years. The kids who are active and would rather be out in the sunshine then in a classroom don't make it. Children must conform or the are left behind, labeled, and drugged. It does not necessarily mean there is something really wrong with the child, the teachers just don't have the time or resources to deal with 25 kids who can't follow directions. An active child causes problems. If your son can't sit still he will have many of the same problems in preschool.