Ashley Yates, 45, from Filton, pictured, who used a spy pen to record images, was sentenced to two years and eight months at Bristol Crown Court.
He had previously pleaded guilty to three counts of making indecent images of children and two counts of voyeurism.
In addition to this, at the hearing earlier today he also admitted a further four counts of voyeurism and two counts of securing unauthorised access to computer material.
His offences came to light after a child found a pen inside a disabled toilet at the primary school. The pen was found to contain a secret recording device.
DI Louise Boyce said: “Yates totally abused his position of trust to feed his own personal desires.
“He set up the recording device in a toilet knowing that both children and adults would be using the facilities.
“A number of his victims were young children, they were also in school – a place where they should feel totally safe and protected.
“I have no doubt that Yates’ crimes will have a lasting impact on his victims and their parents. All have received specialised support and will continue to do so as long as they require it.
“This has been a complex investigation and one which we have worked closely with partner agencies.
“I hope this case emphasises our dedication to robustly investigating crimes effectively and with our partners.”