A cleaner filmed two pupils changing out of their swimwear at a school in Dubai, the criminal court heard.
On March 27, the 23-year-old Nigerian defendant snuck a mobile phone into the school and hid in the changing rooms to film the two brothers, aged 7 and 9, as they dressed.
One of the boys saw the defendant filming them and asked him what he was doing but the man did not respond.
The Turkish boys told their teacher, who then told the school principal, about the incident. The principal called police after confronting the cleaner who denied filming the boys.
The boys' mother said the principal told her what had happened when she picked her sons up from the school in Al Barsha the same day. She said her sons told her what happened on the way home too.
"When I went to school, the principal asked to talk to me and informed that he reported the matter to police and that I should expect a call from them," said the mother, 43.
She said police called her the same day and asked her to give a testimony at a police station.
"I told them what my kids told me," she said.
The cleaner's phone was confiscated and prosecutors found the video of the naked children.
At Dubai Criminal Court on Sunday, the defendant pleaded guilty to a sex assault charge.
A verdict will be issued on May 27.