My younger's teachers say, "he is a bit on the active side." In Teacher-speak, that means he is a bit tough to control in the classroom.
I've talked with a lot of people and done a lot of research when one teacher recommended that we get him tested for ADHD.
If your son has a hard time concentrating, if he cannot sit down for 15 minutes on a project that he loves, then you may want to get him evaluated. My 4 year old son will sit for 20 minutes working on a puzzle or drawing, etc., so I thought it might not be ADHD. I've asked other child care givers who know my son and all said that they do not think he has ADHD.
From all of the information I've read, if he can sit for 15 minutes on a project, you may want to think about changing two things: 1) diet, 2) sleep.
There is a lot of annectodal evidence that shows foods with a lot of preservatives, food colorings, partially hydrodenated oils, and corn syrup has a negative effect on our children, especially boys. It causes hyper activity, low attention span, and behaviors that some would say looks like ADHD. It is just not good for their little bodies and causes negative behaviors.
Goldfish, crackers, chips, low-end granola bars, many cereals all have these items. Take a look at what he is eating and purge all of these items immediately.
Cut back on items with a lot of added sugar - only 100% juice or water, absolutely no soda. Remove fast foods from the menu - no McDonalds, no Starbucks. Remove processed foods - no prepared items. Go back to fresh fruits, vegetables, simple dishes prepared at home.
I'm a working mom, too. I hear you. ;-)
4 year olds still need their nap during the day. If he is skipping the nap, you should seriously consider adding that back into his day. It does not affect his nighttime sleep pattern if the nap ends before 3PM. So, after lunch, a nice 1 hour to 1.5 hour nap would do the body good. Do you know the feeling of being wired because you stayed up late the night before? I become cranky, irritable, negative, etc. Sleep is a good thing for our kids.
When my son starts to show signs of crankiness, I actually begin to calm down and become quieter. I ask, "do you feel ok? are you tired? hungry?" When my boys are well fed with a good nights sleep, they are angels. When they are either hungry or tired, watch out.
My DH used to get mad when my son started to misbehave, but, now he asks immediately, "are you hungry or tired?" 9 times out of 10, they say that they are either hungry to tired. Then after we feed them or let them rest, we talk with them about identify their feelings and expressing it in positive ways. Now my older can tell us that he is hungry or tired. My younger is learning, although it is usually in the middle of a wail, "MOOOOOMMMMMYY!! I'm soooooooo tired." Hey, little steps forward.