Special education services vary so much by state, even by district there are huge differences...
Kincaid (who was diagnosed with dyspraxia at 18 months, global developmental delays at 18 months, ASD (they never specified it) at 2 1/2, and re diagnosed with global dyspraxia at 6 when he lost his ASD diagnosis) was put in pre-school when he turned 3. In Michigan it was a specifically special needs pre-school, kids were in self contained class rooms there, and it was 6 kids, 1 teacher, 2 aides, then there was always 1 therapist (speech, phyisical, occupational, behavioral) in the room at all times too, so it was 6 kids to 4 adults. But it was 3 1/2 hours, not all day, and it was m-th and it went on the normal public school schedule (laborday till early june). In denver (cherry creek schools) it is a mixed class room, he was actually one of only 2 kids in his first pre-school class here that had special needs, all the others were esl kids...it was also 15 kids to 3-4 adults... In his second pre-school it was a much better mix, probably 5 kids there for special needs and 7 "typical" children, also there were at least 5 adults at all times. For kindergarten here in this district EVERYONE is mainstreamed, there are no self contained classrooms before 6th grade, it doesn't matter what the delay is...kids who can't walk, eat or talk are still in normal class rooms, they get pull outs obviously, and depending on how severe the delay (and behaviour issues, like running away, violence, etc) is they have 1:1 aids, but it's completely mainstreamed. Kincaid receives 16 hours of therapy per week at school (out of 30 total class room hours(including lunch and recess) per week, so he is getting 1:1 or 3:1 therapy for more hours than he is actually in his kindergarten class) this year, and that will be bumped up to 19 hours per week starting next year when he is in school all day. Right now he goes all day, but because we pay for the kindergarten enrichment program.
Travis is 2, he'll be 3 in August, he was diagnosed with autism (moderate-severe) at 2 1/2, after about 9 months of ST (the only thing he qualified for at his first eval a year ago) had no results and his therapist, after spending so much time with him, saw a lot of other issues. He will be transferred to pre-school through the school district in August. There are 30 slots district wide for a specific autism program for pre-schoolers...and he qualifies for one of those spots, it will be a 7:5 ratio, but it will still only be 3 1/2 hours 4 days per week...he'll stay there till K.