We going for kindy with our 5yo ds (jan bday). Our school district has "centers" - K-2, and the principal said that they'd still have to differentiate even in 2nd. And since his social skills are at age-level (according to a questionnaire that I probably shouldn't have answered quite so truthfully!), we'll give kindergarten a try. Re: social skills - he's our only child, and i'm a SAHM, so since he has no interest whatsoever in dressing himself, i never made that a big deal and just helped him get dressed if we ever wanted to get out of the house on time. Note to self - next "social skills" questionnaire, answer if he "could" do something, rather than if he "does" do it!
I think for our DS, the transition to full-day school is going to be a big shock, and he does need to ease into the whole school thing, so kindergarten should be OK. Also, he has no interest in learning how to write, and i'm sure the kindergarten teachers can teach that pretty well.
