Hope your dance shoot went well!
But, to have some more info out there "just in case", the way I've handled my dance schools is almost exactly the way that photo_chick described.
My biggest school is about 90 girls X 2-5 costume changes each. I start on Saturday from 4-9 PM for the older girls and we're back at it Sunday morning at 8:30 until 7 or 8 PM. Schedule is completed several weeks before and all students know when they're expected.
I have a staffed table with cash box to take payment and be sure all order forms are completed.
One gotcha to look out for is the name of the dance class. Some parents will write Tuesday 6:30, another Tuesday Ballet, another "Dream", yet another "A dream is a wish", and someone else "Wish". Gets confusing so standardizing that is on the list for next season.
I take a shot of the order form in front of each girl so I can identify the order later, and I include my color checker passport in the shot so I'm sure to have it with each lighting change.
I keep moms out of the room but the studio owners are on hand to chimp and approve/disapprove of the shots. Moms trust them so it's usually OK.
Studio owners / instructors do most of the posing because of their familiarity with the choreography in that particular number. I make some tweaks but it's not usually anything major. The older girls are usually pretty good on their own.
I replaced my 10x20 background with a 20x20 because I got tired of patching it in photoshop for the group pictures. Well worth the investment.
Fortunately the schools I work with let me shoot in my style and appreciate the extra effort involved.
My daughter has been dancing so long that I've got plenty of flat lit shots of her in her costume, standing against a boring background leaning on a Grecian column in front of a vase full of flowers.
Here are a couple from last season.
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