We'll be there Oct 13-18; we are so excited!!
We usually go in the summer, but the last three years, we've take a quick trip the week AFTER Thanksgiving to see the Christmas decorations,
MVMCP, Candlelight Processional, etc. We've never really had a problem with school groups in Epcot. We've seen them, but they really didn't affect "crowds".
However, last year, as we were walking around World Showcase, my little girl was working on her mask at each of the countries. There was a large group of kids that would come running up at each kidstop to get their paper stamped for school. They were a little rude, lots of pushing and shoving on each other, and no consideration for the kids that were already there working on their mask. (Part of their school assignment was to get this sheet stamped by each country. But the kids just ran up and got the paper signed; they really didn't look around or try to learn anything about that country.) Once they were done with their stamp, it was nice at the kidstop stations.
Again, I really don't think they affected crowds at Epcot. Most things were still a walk on; and we spent a lot of time sending e-mail pictures to friends (there was no one in line at the time).
Enjoy your trip! Hope to see ya there!!!