I do think that a big class size can work well. In our very highly-rated public school system, all four of my kids have been in bigger and smaller classrooms (and yes, over 30). My two oldest are in college now, and honestly, what has made the difference more than class size OR teacher is the principal. Having a principal who advocates for differentiation and acceleration has been key. That way, it works EVERY year, not just the year you get a small class or a good teacher. My PG dd20 got little-to-no differentiation. My ds9 is in 3rd grade and is working out of the 6th grade math book, after being put into the 5th grade regular math class and finishing the work. The principal worked with the gifted coordinator and the classroom teacher and came up with a plan from "Developing Math Talent" to help our youngest grow in math. That made more of a difference than a small class!

Here are my thoughts about what you need to know:
1) what is the state cutoff for class size. What happens if they go over in November? Will they split the classes, add an aide, etc??
2) How welcome are parent volunteers? My ds11's 4th grade class had 32 kids but the teacher had tons of differentiation and parent volunteers every single day for core subjects.
3) Can your dd subject accelerate to a different grade for any subjects?
4) With only one class, how is differentiation handled? Can your dd do independent projects? Can she have a mentor? Can she get *different*-not extra- work?
5) if your dd is on a 504/IEP plan, can you meet the case manager? How are special needs handled? Can you talk to the potential teacher to get his/her take on things?
6) If your dd thinks that school is a waste of time, also check things like homework policy, "busy" work, etc... One of the things my boys love about our current school is that homework is limited and rarely busywork. If you do well on spelling, there are no "packets" of work (if you start to fail, then there are). If you know the math, it's okay to say, "this was really easy, so I just did the first three problems, and then I felt like I knew it." There's a lot of latitude for good students.

As far as homeschooling, I do think it can work wonders, but I wouldn't do it just because you feel you have to. Your dd can go to school and do a very minimal amount of "extra" at home and still come away with a lot. Some days my sons get socialization, listening and orchestra out of the day, but that's okay (most days they do learn :)). I honestly know it wouldn't work for me to homeschool and I think we'd all kill each other... well, no, my kids are better-natured than me. I'd be the screaming lunatic.

Hang in there and go to the tour with an open mind. I know class size is important, but it's not all there is. A good school with bigger classes might trump a smaller disinterested school.
Good luck- Theresa