I would say it depends on what you're expecting for the pre-K to bring you. And also, is the public pre-K all day or just half day? If it's just half day, I'd probably try it. If all day that could make him seriously bored. DS4.5 started public pre-K in the fall after he turned 4 and went in already knowing the whole year curriculum (and beyond) but we really only sent him in for the social interaction and to get used to being in a formal school setting. He basically goes to school to have fun and then he afterschools himself at home. It has worked great, with no complains on his part until just this last week when the teacher mentioned that he started complaining about being bored and not learning anything. I think he's entering the age when he's starting to realize he's at school and should come home knowing new things. But other than that, he has been very happy. But again, it's only 3hours a day so it's short enough not to get too bored.
