Nigel Leat, 51, filmed shocking scenes of abuse against five carefully selected girls over the course of five years at Hillside First School in Weston-super-Mare, Somerset.
His victims' families listened in disbelief.
Some relatives broke down in tears in the public gallery as the sentencing hearing at Bristol Crown Court heard details of how he would molest the girls as they practised their reading aloud in class, getting them to perform sex acts on him at the same time.
He could be heard in films referring to the girls as "sweetie pie" and "darling" and asking them how much they loved him.
The videos, in most of which Leat could be seen, showed girls were abused in the school's staff room and a resource room.
He would film himself touching their bottoms and their genitals, including when they were changing their clothes to go outside.
He also wrote letters to them, asking them to perform sex acts on him.
The father of two, who wore dark glasses and sat with his head bowed in the dock, initially denied all the claims made against him. But he confessed after police found the perverted films he recorded on his home computer.
Simon Morgan, prosecuting, told the court: "It is clear that these children had become well versed in doing what was expected of them.
"These were a myriad of offences over several years against exceptionally young children.
"The defendant took risks - he arranged the rooms in such a way as to avoid detection. The evidence shows that he took these opportunities to abuse these children."
Leat, of Bloomfield Road, Bristol, has admitted 36 sex offences, including attempted rape of a child and sexual assault on children.
The court heard that the popular teacher, who spent 15 years at the school, was warned in 2008 about being too "tactile" with the girls in his class by the school's deputy head, as staff were worried that it might leave him open to accusations of improper behaviour. No further action was ever taken.
The offences took place between September 2006 and December last year on five children referred to throughout the hearing as children A to E.
The court heard that he picked out children to receive special attention from him, including help when they struggled with reading.
He would place a camera under his desk and call them up, recording as he sexually abused them. In many of the videos, which are up to 10 minutes in length, other children can be seen or heard in the background as he performs the acts.
Several times he appears to have been disturbed by either children or other staff members while engaging in abuse.
Most of the videos showed that the girls willingly complied with his demands, because, the court heard, he had made it seem like normal behaviour through his grooming of his victims.
One video showed him abusing a child and then trying to force her to perform a sex act on him, putting his hand forcefully on the back of her head when she refused to comply with what he wanted.
He was eventually arrested after one of his young victims, to whom he gave gifts, admitted to her mother what Leat had done to her and the police became involved.
At a hearing at Bristol Crown Court on May 5, Leat admitted 23 charges of sexually assaulting a child under 13; eight charges of sexual assault by penetration of a child under 13; one charge of attempted rape of a child under 13; one charge of voyeurism; one charge of causing or inciting a child under 13 to commit sexual activity; and two charges of possessing child pornography.
When police arrested Leat, a keen birdwatcher and cyclist who had a long teaching career, they discovered around 30,500 indecent photographs and 720 indecent movies in his possession on a computer and memory stick. The collection included one video of a child aged between seven and eight involved in an indecent act with an animal.
The court heard that one of his victims' parents had been worried about his behaviour after she left his class and he asked if the girl had a webcam so he could keep in touch. But no concerns were passed on to authorities.
Nicholas Gerasimidis, defending Leat, said his client had shown "genuine repentance" over his actions, which he said had been shown by a psychiatric report to have started when his 27-year marriage became "asexual" 10 years ago.
"He is truly ashamed of the whole business," Mr Gerasimidis said.
"This man was in a school, teaching, and parents who sent their children there did not send them there to experience what they did at his hands.
"It has led to the disassembly of his whole life. He is to be divorced from his wife and his children want nothing more to do with him.
"It is to his shame that he acted as he did. Through me, he wants to make a public apology to the families he has devastated."
Attempting to dissuade Judge Neil Ford from imprisoning Leat indefinitely for public protection, Mr Gerasimidis added: "It might be said that if he was not in the position that he was in (as a teacher), this interest (in young girls) may never have had an opportunity for expression."
Speaking outside Bristol Crown Court, Detective Superintendent Geoff Wessell said: "The court heard the full extent of the behaviour of Nigel Leat in the most shocking detail.
"It is quite clear that the court has heard that he is a predatory paedophile who has broken the trust and confidence of both the parents that sent their children to the school and its staff."
Judge Ford adjourned the hearing until next Tuesday before passing sentence.
