I have been incredibly happy with our SECOND preschool. We started out in Montessori, and while I think my son had FUN, and I liked the teacher very much, the whole concept is that the kids decide what they want to do during the day. They are supposed to learn what they're most "open" to learning at that point in time.
Great concept, loved the idea, but my son didn't appear to be actually learning much. Of course, who knows how much he picked up? So hard to say.
We have now enrolled him at Creative Scholars Preschool, which is on Elston between North Avenue and Armitage, which is pretty close for you. WE LOVE IT. It is a private school with no church affiliation. Every single day we're sent home with actual things my son worked on: paintings, tiny pieces of paper from practicing cutting with scissors, coloring sheets, paper strips with letters he wrote in a row, etc. He's just turned 3 (2 weeks before school started) and is learning to write his name and spell short words already. They have a note with lesson plans each day so you know what the kids are talking about in class. I'm thrilled. They get music and foreign language (not just the usual Spanish, other languages, too) as well as the standard art. He has been there since the beginning of September and now knows the days of the week and months of the year. It's only been two months! There are just so many things I'm happy with, not the least of which is how small the classes are (my child's class has 8 kids).
They have an INDOOR playground, so the kids get to play all winter with no coats, and we don't lose that important running around time when it rains. (The indoor space could be a negative, as well, since they don't do much outside when it's warm out, but I figure I take my kids to the park myself when it's nice, and I'd rather be assured he gets to let out some energy while he's at school all winter!)
And they also have indoor parking for drop off and pick up, again a huge benefit during nasty weather.
Check out their website and if you take a tour, please tell them Ryan's mom (A.) referred you. Both directors (Mary and Lisa) know my son & I, they're actively in the classroom with the other teachers, not holed up in an office all day. I get a referral credit. But I would do it for free, too. :) Feel free to contact me with any questions, we've been so happy with our school choice!
Oh, and they do offer full AND half days (morning or afternoon), and the choice of 2, 3 or 5 day a week, so it is very flexible which you were looking for. We only do half days, it's a nice transition for a younger child if you don't HAVE to use full day because of your work schedule. (I realize you're a SAHM - I am, too - but other people will read this post that are not.) The full day kids (and morning half days) get an amazing hot catered lunch. It's all organic everything. Those kids are getting a better lunch than I am! LOL!
Last, you said you were looking to start in September, but as your pregnancy progresses, you may find that you would like a break from your 3 year old sooner than next fall. It's tiring having a baby with another young one to watch. Another benefit to Creative Scholars is they have year-round enrollment, so you can start anytime after your child is potty trained (and older than 2-1/2 which yours already is). When we started looking at preschools so many of them had December or January application deadlines for the FOLLOWING fall, it amazed me. I still applied months in advance for our spot at CSP because I wanted to be assured of my choice of days and morning or afternoon, but if you're more flexible about the days/times, you can apply and start the next day. Trust me, a few months into your pregnancy this could be very appealing. Best of luck to you!