This past Monday I attended an Irish session, I do this weekly. From 7:00 pm to 9:00pm it's a slow session (no singing ever happens here) after that it's a regular session. There were plenty of teens, maybe 5 or 6 all very good, plus a number of college kids (Boston College is close by) 1 an all Ireland junior fiddler, sometimes there may even be a couple of good to very good pre-teens (the average # is probably 20-25 playerss at the height of the session). They get called on to lead or lead as they see fit & play with their elders (the oldest regular, a bones player, probably in his 90's) who treat them as musical peers. Musicians that can't keep up with the session either wait until there's a tune they can keep up with or sit back for a slow air otherwise, they only play in the slow session. As for singers, you sing when you get invited, once a woman used a sheet, she was never asked again. The older group are musicians that are maily Irish born & bred & learn their music in the old way, some are from the old Dudley Street dance tradition of the 40's & 50's.
I bring this Irish session into the discussion because I believe what I'm presenting is the norm, at least for Irish sessions (except for the age) in the USA that I've heard of. Why is it that this is common & OK for Irish sessions but some think it's not ok for singing sessions? What are the different dynamics? Irish sessions are a bit closer to a living tradition, no? Do those sessions retain a higher quality of musicianship while encouraging players to practice at home & to learn their music in a traditional oral way while not discouraging them at the same time. Suppose they encouraged beginners to bring in sheet music & they can learn as they go, how would those sessions survive? They would not!
The more you have books & notes, the more the singing session becomes a practice or a learning session, a little is ok, sometimes in someplaces, IMHO, maybe in many cases but not all, to much & you drive out the backbone and you end up dumbing it down. Is it fun when it becomes a learning or practice session? Fun for who? Want a teacher, where do you go to find one? At a session? Is that where they teach? Where do you go to learn or practice at a session?

Barry