We had several teachers doing that in our ES. Seemed to work out well. The flaw is the kids could not continue in the cluster for middle and high school so they had to make new friends.

Anonymous wrote:I know of a few teachers at our school with COSA for their elementary students to attend where they work. They still need before and aftercare though for meetings and the kid can not stay in cluster for middle school.

There are a bunch at DC's highly regarded school. They are not in before care or aftercare as far as I know because our child is in both.
I think it works out nicely for everyone. It's nice to get to know the teachers as parents and since their children attend they come to all the functions and it's great to have them there. I think it creates a stronger community. I thought it was very common at elementary schools that are not overcrowded.