
Putting 7-8th graders with adults is not a good idea! We have a separate 7-8th class (6th is in rotation). Although having youth with adults for special things can be good, in an ongoing format I don't find it helpful. The youth either feel intimidated or are directly put down by the adults. Plus they need to be able to bond together, guided by adults who know and love them for who they are. If they're in with the adults, that probably also means they're with their parents and that's also not always helpful. Yes, we want to foster good relationships between our kids and their parents, but CE classes aren't the proper forum (other than special events).
On the 6th grade in church-do you mean they're too young to be in worship? Hardly. Children learn to worship by participating and observing the adults. (Read: No separate children's church) If your children in 6th and under are not in worship now, how can they be expected to know what's going on or to continue in worship as they grow?

Just when you expect them to be in worship, they'll avoid it because it's too unfamiliar, compounded with the whole questioning thing that adolescents do.
Our church welcomes those in first grade and up in worship. All our children and youth participate regularly in choir, handbells, etc. As they prepare for worship, we also teach them about the different parts. We have a fairly 'high' and 'traditional' liturgy for a PCUSA congregation-BUT that is a GOOD thing when you want to help your younger members follow and understand. Less traditional forms of worship are also attractive, especially when the kids have a part in planning (ours do from time to time). The point is KIDS NEED TO BE IN WORSHIP!