How many days per week of preschool?
My 3 year old isn't in preschool yet, but I think it would really put a damper on all the cool parent-child activities we do together, particularly if she was in for more than 2 days a week. I had her in 2-day per week summer camp this year, and it did feel like we missed out on a lot of playdates, beach days, etc. because we just weren't as flexible. I think that next year (she'll be 4) we'll put her in 2-day. I know she'll love it and want to go every day, but I'm just not willing to relinquish her that much yet!
BTW, our local Waldorf school does a neat parent-child preschool type playgroup once a week. Something like that might be cool to check out, and you could put him in a preschool camp program to get him used to things over the summer, right before he starts his 5-day program. (Not trying to urge you away from preschool, just offering some alternatives in case you're interested )
Definitely child-dependent. I'm looking to get DD into a program next fall when she's 3, hoping for Montessori, but depending on which school we get her into we also will have the option of full or half day. For us, DH works full time, 2 jobs, I do part time work/part time at home and while I work FIL watches her. I've got my issues with him watching her for various reasons posted in other threads, but from a physical perspective, he's had 2 heart attacks and has a hard time keeping up with her now, so I can't imagine him keeping up with her at 3. She's SUPER social, absolutely loves interacting with people (complete social butterfly and total opposite of me), yet is very independent and can play on her own for far longer than most kids her age I know. She's also smart...too smart. I feel like keeping her home is more limiting to her than sending her to school for a few days a week or even full time. I guess the deciding factor for us on length of time will be whether or not she's still napping at that point. So things to consider:
1. Independence level
2. Need/desire for social interactions
3. Nap schedule
4. Type of school program - is it tailored to individual needs like Waldorf/Montessori, or do they lump the kids together with less wiggle room for individual needs and which would be more suited for your LO's personality
Recently, we decided to put our 1 year and 8 months old baby in a part time preschool - 1-5pm, 5 days a week, but it didn't go too well. Our son was getting sick about once a week and stayed at home healing from colds more than went to school. So we are taking him out of the school and keeping him at home with us at least until next year. Even though what we heard from other parents and the school staff is that this is perfectly common, meaning that babies get sick when exposed to other kids. This was a stressful experience for us, and I think that the longer parents can stay with their kids at home, the better.
I think it's very case specific. Our son got a place at the Waldorf preschool when he was just over 2 years old. They only had a 5-day-a-week place from 9-2. Being Waldorf they are insistent about the regular rhythm thing so there was no other option but same schedule 5 days a week. We were reluctant to have him there so much but we took the place because he wouldn't have gotten one the next years and it was the only chance for this preschool. He did fine. BUT....first thing was a very long and slow and gradual adjustment period. It lasted at least a month and went from one hour there with me, to gradually me going away and him staying a couple hours, to me picking him up at noon, to him staying for nap til 2. The other crucial thing is: he was in private daycare (four kids at one person's home) for a year before that....also with a very long and slow adjustment phase....so he was used to being in a social daycare situation and it must have made it easier for him to transition to his current preschool.
If your child is brand new to daycare, I would try 2-3 mornings a week and insist on a slow adjustment phase if needed. I think the way many preschools just have you either drop them off cold or stay one day for one hour and then expect to just leave them there is nuts. Even if it seems ok at first, the novelty often wears off and you have some sort of drama at drop off or other behavioral problems a few weeks or months in. So I am a big huge fan of a slow gradual adjustment phase and I wouldn't send my kid to any preschool that made me just drop him off, screaming or not.