My DS was begging to go to school (he has an older sister). We decided to enroll him in a nearby preschool that DD had liked. This school emphasizes academic-type skills. DS was 2 yrs, 9 mos. and toilet trained so we were able to talk them into placing him in the 3 yr old class--kids who would be in his Kindergarten cohort.
We had mixed results. He did not fit in socially and was bored academically. It wasn't horrible, but it wasn't great, either. DD had loved going to that school, but it wasn't a good fit for DS.