High lead levels are very bad news. I have 4 children, all of whom had rising lead levels in the past 8 months. Lead poisoning often goes undetected. It shows itself in little ways, that, in my opinion seem to mimic ADD/ADHD (it has even been shown to lower IQs.) You can't see lead, so I don't think it really matters that someone 'looked over' your house. I know testing is expensive (starting at around $500) but it could be very beneficial to your son. Also, have you been experiencing any strange symptoms? Before we moved out of the 'lead house' I used to suffer from terrible cluster headaches-we only lived there a little over a year, and I had never had headaches before. Lead poisoning can come from lote of things, and there is a lot of info to be had on it, people just choose not to pay attention. I know more about lead than I ever wanted to! We had to move because the lead was spread too much throughout the house, we basically would have had to tear it down and start over, and even then there could be lead particles in the DIRT outside the house to worry about!
Lead is toxic because when ingested or inhaled and absorbed, it can harm virtually every system in the human body, especially the brain, kidney and reproductive systems of both males and females. Whether that damage is temporary or permanent remains a source of scientific debate. Lead harms so many body systems because it disrupts enzyme systems mediated by other metals important to the body - iron, calcium and zinc.------------------------source: http://www.environment.nsw.gov.au/leadsafe/leadinf2.htm