Ours is more like a thematic discussion group divided by classes with separate teachers. It meets once or maybe twice a month during coffee hour. Kindergartners and such do coloring. High schoolers have lessons, on thematic topics (one week was even focused on Christian understandings of sexuality - I think parents were encouraged to come to that one too) and a Q&A led by the priest.
That is my experience in Greece as well. Meetings are weekly after liturgy, whether on Saturday or Sunday. Topics are not as advanced, mostly because few kids over 15 keep going, but at least for me (who kept going until 18) the chanting practice was well worth it.
For anyone competent enough in Greek, this
is a good collection of resources from different parts of the country.