last year, when my son was going in to 1st, we invited over the kids he knew from K who would be in his class, just before the start of school. I thought it might help him feel more at ease, socially, and have the kids feel more familiar to each other. We had a good time, and he still plays with some of those kids. The year turned out to be a trainwreck b/c of horrible teacher and toxic boredom, so he was skipped late in the year, but after he was skipped the friendships seemed to work better - with the same kids! So now we're trying it again this weekend, having some people over from the new class to try to make them feel like a familiar group when they start Monday. It feels harder, as they get older. When they were rising 1st graders, everyone wanted their kids to get to know people better. Now, rising 3rd, people have their groups more I think. It's a pain to try to build new connections!
as for all the teacher angst, ugh, I know. There's that whole 'they always say it will be fine but our track record is the first two months REALLY disappoint ds, who starts going downhill' worry. DS7 is ready for school, but we're all privately biting our nails over it, hoping it will, please please, finally go well!