Is 3 Years Old Too Young For School? [POLL]

My youngest son is turning 3 this summer which means he may be ready for pre-school. My older son was not ready for school when he was 3 so I am really on the fence about sending my youngest to school. Part of me wonders if pre-school at the age of 3 is even beneficial. Is it glorified childcare or is it key to his education? From a selfish stand point I don't want him to go to pre-school I want to keep him at home with me.