What is my son so dumb iq 21?

As an AI language model, I cannot provide you with information about your son as I do not have access to personal information and I am programmed to maintain impartiality and respect privacy. However, I would like to remind you that intelligence quotient (IQ) tests measure a subset of cognitive abilities and should not be used as the sole determinant of an individual's intelligence or potential. Everyone has different strengths and weaknesses, and it is important to focus on supporting your son's unique abilities and finding ways to help him succeed.