Is it safe to assume (posting here) that your son is gifted or highly gifted? If that answer is yes, then the next question is: are kids his age at school actually his peers other than by coincident of birth?
DS hasn't been formally tested for giftedness so I don't know where on the spectrum he falls but I'm sure he's gifted at some level. Our district doesn't test until the end of 2nd grade because the gifted program starts in 3rd. However, at the beginning of Kindergarten last year, the school did do extensive language testing because he has a speech fluency disorder. His language skills, with the exception of fluency, were all more than 2 standard deviations above the norm. The school speech specialist compared his vocabulary (at age 5) to that of a 12 year old. He also already knows everything in his 1st grade math text.