Matthew Smith paid £67,000 for sexual photos of children as young as seven and was described as a "master manipulator" in court which also heard how on one instance he paid two young boys "thousands" for sexually explicit material.
The 34 year old from East Dulwich pleaded guilty to a total of 22 charges after investigators raided his London home last November to find him asking a teenager in India to send him sexual images of a younger child.
Mathew was fired from Thomas's prep school on Battersea High Street, the £20,000 a year prep school that taught Prince George and Princess Charlotte after allegations first emerged last November.
He had spent some time in Nepal and India working in orphanages and NGOs between 2007 and 2014.
He later moved back to the UK last July and began working at Thomas's prep as deputy head teacher and head of pastoral care, before he was sacked amid allegations.
Chat logs from Mr. Smith showed he would order young men to perform sexual acts on boys and send them images and videos as examples of ones he would like to see re-enacted.
He also gave one of the teenagers advice on how he would befriend children and build their trust with the aim of abusing them.