I agree that very young girls with the 17-18 yr old girls would be difficult because of language and break chats, however what do you do when you are a VERY small gym. I'm talking just enough girls for barely 1 team? You have similar level tumbling throughout all the age groups. If you put together a junior team and it has 1/2 of your members so maybe only 12 girls, do you want them competing against a team with 24 or more? It's not fair to your girls. My gym has about 25 members right now, and as much as I'd prefer a 12+ or 14+ senior team, I may not have a choice since we only have about 5 or 6 12+ girls. As a small gym sometimes you have to accommodate the members you have how ever you can. Losing the senior aged girls because we decided to only have a junior team or vise versa would be a huge impact on our tiny gym. It's a very tough decision, and you have to take a LOT into consideration when making the level/division choice. I don't want to hold anyone back if they have great skills, but I also want to make sure EVERYONE'S best interests are kept in mind.