I'm LOL at the 18 or 19. I was married at 20 and I can't imagine a year prior (really 5 months) having to get my parents permission to go alone at Dland
18YOs are grown ups and can support themselves and live on their own, I can't imagine they would need permission to tour Dland alone 
To the original question. I would say probably 13-14YO in a group. -- I know Dland is a popular 8th grade graduation trip around here (Socal) and they just drop you off and say see you at the bus tonight.
18YOs are grown ups and can support themselves and live on their own, I can't imagine they would need permission to tour Dland alone 
To the original question. I would say probably 13-14YO in a group. -- I know Dland is a popular 8th grade graduation trip around here (Socal) and they just drop you off and say see you at the bus tonight.
Being in DL with my DH and all my kids was so awesome. My oldest daughter, a few times went to get herself a drink while we were close by and went into a couple of stores in downtown disney while i sat and waited for her, exhausted...To me, the best part of our trip was the incredible family time we spent together, on the way home, i asked my kids to rate our trip, and even my 15 year old daughter said a 10(wow, and that was spending almost every minute every day with her mom, dad, brother and sister
) If we had gone with another family who had kids the same age, i would have had to allow her a small amount of time to go off with her friend, but she would definately have been fine...