I have a younger one a bit like that. He is very funny and everybody thinks he is adorable. I want to get him tested before he starts school - say 4 years 11 months - but I am afraid he will give deliberately stupid answers on purpose. His is stubborn, argumentative and prone to tantrums but oh so cute when in a good mood.

ANyway I say test if possible. I honestly never would have guessed my older son was >99.9 percentile and I still have no idea about the younger one.