It is a good idea for dancers to have a dance bag so that they come to each class prepared. When I say dance bag, it does not need to be a specifically bought dance bag as any bag will work.
Ideally, tiny tots should enter the dance studio already wearing their dance attire with their shoes on and tied, so their dance bag shouldn’t really contain anything except the necessary change of shoes and a water bottle. It is better not to put too much in the bag so there are not distracting things that have the potential to get lost. A dance bag for a tiny tot is not completely necessary, but it does help from shoes getting mixed up between students.
As the dancers get older, they will probably want a few more things in their dance bag. If they are taking multiple dance classes, they will need the various shoes with them. It also might be a good idea to have a dance type sweater for ballet class for when the studio is cold. I would encourage having some accessories for their hair to ensure that it can always be pulled away from the face. Depending if the dancer is taking pointe or hip hop classes, they may need some bandaids for toes to help with those pointe shoes or even a little towel to help with sweat. If a student is taking multiple classes, fresh water is always important and a light healthy snack. One of the great benefits of participating in dance is that there is no heavy equipment to drag around so any small bag should be able to hold all the necessary items!