Avoid schools runs, especially when there's dozens of 4x4's / people carriers about all carrying one kid each for a half mile trip.
Tell the truth mate, this fella's probably bumped into one of those ' had an accident ' types, and is now trying to pull a fast one i.e he's now developing headaches, sore neck, bad back, anxiety attacks etc etc.
Tell them you barely touched the car, and both parties drove off realising there was no damage done. As other people have already said though consult a solictor / your insurance if things get tricky.