Thomas David Ball, 30, hid the camera in the bathroom at the school he worked at in the summer of 2018, York Crown Court heard.
When the device was found, Ball, of Over Road, Atherstone in Warwickshire, denied all knowledge, but extensive police investigations revealed he was responsible.
Appearing before the court on Wednesday, Ball pleaded guilty to voyeurism, three counts of making indecent images of children, one count of taking indecent images of children and one count of possessing indecent images of children.
He was jailed for 20 months.
North Yorkshire Police Detective Constable, Adam Fenwick, said: "Thomas Ball was in a trusted position of responsibility which he has blatantly abused for his own gratification. When the device was found he attempted to deny all offences but thanks to extensive digital evidence we were able to prove without doubt that he had purchased and planted the camera.
“He is a cold and calculating individual who carefully planned and premeditated his actions. He clearly poses a significant risk to young people and we hope his sentencing will give some closure to the victim and their family."