These three young Junior High Schoolgirls are Miko, or shrine maidens, and are taking part in the procession of the mikoshi at a matsuri. Before the procession they had performed Miko-mai, a sacred dance in the shrine.
Miko also assist the priests with ceremonial duties as in the photo below where a miko is performing Oharae, a purification ritual. There are a few female priests in Shinto, but not many.
Another type of miko no longer existing were the wives of Shugenja. The miko would go into a trance under the control of her yamabushi husband. Miki-san, the founder of the Tenrikyo religion was functioning as a stand-in miko when she began to have trance. Shamanesses and priestesses were probably the norm in ancient times before the influence of Buddhism.