It's important that both you and your child's teacher(s) have input. You should both be asked to fill out a behavioral observation form so the person doing the evaluation can have a clear picture of how your child is behaving both in and out of school from both your points of view. Ideally, the person doing the evaluation should also spend some time observing your child in situations where he's having trouble managing his behavior.
If medication is recommended, follow-up observational forms from both of you should be completed on a regular basis to see if the medication is having the desired effect. You need to find a practitioner you can trust who will stay with you through treatment. And medication is usually not the only treatment recommended although many studies have shown its positive effects. A good behavior-modification program, social-skills training, and good structured teaching can also help when combined with medication. I'd recommend that you call CHADD (Children and Adults with Attention Deficit Disorders), a support group for parents and professionals. The toll-free number is 1-800-233-4050. Their website is www.chadd.org. You can find out if there's a branch of CHADD in your area and also get a referral for an evaluation from a professional who specializes in diagnosis of ADHD. You need to work with someone who has lots of experience diagnosing the problem and monitoring the treatment.
You also indicate that your son is having problems learning. Managing your son's behavior alone will not necessarily improve his learning. It may be necessary to modify his instructional program in school as well. Make sure that an educational evaluation is also part of your plan. That can be done free-of-charge by a professional team in your school or school district. Ask the play therapist or school guidance counselor how to get the process going.
When you meet with the play therapist, ask her what modifications have already been made to your son's program in school. What strategies have been successful and which ones did not work? How does he compare with other children in class?
The most important thing you need right now is to find a person you can trust who can guide you through this process.