I visited with a junior high librarian today, who showed me this setup in her back room.
She has 3 10-slot charging stations with little short cords to charge student devices. Students come to the circ desk and check out a spot for their phone or iPad. The librarian takes their device, plugs it in to one of the slots, and then checks the card out to the student. This gives 2 security checks before the librarian hands over a student phone after charging--the student must have the claim ticket, but student info and a photo pop up in the circ system when the card is checked in and can be verified by the librarian.
Teachers and students are really pleased with this program so far. Students appreciate that it gives them a safe place to charge their devices, so they don't have to leave them unattended near a wall outlet. Teachers like that it keeps students from crawling around on the floor searching for outlets, and keeps them from being responsible for any theft that occurs when phones are plugged in and left to charge.
The charging stations run about $70, and 6" cords are purchased separately. She just has lightning and micro USB available right now, so if students have upgraded to USB-C, they can provide their own cable, provided the other end is USB-A.