What age is it ok for kids to go to clubs without a parent?

[Jasnem]

My DDs are 5&6, and want to go to Rainbows. DP is insisting that they are too young and I have to stay with them.
I think he's over cautious/paranoid, what do you think?

well my little charge started ballet at 2 3/4. Parents arnt even allowed to stay in the room or watch (except for their 1st ever class)

all the girls in her class at the moment are less than 3 1/2! and they have all been left for the past term!