A teaching assistant has been charged for sexually assaulting a 5-year-old boy inside a Brooklyn classroom, police say.

Alameldin Abdelrahim, 62, was arrested and charged Thursday with three counts of sex abuse and one count of endangering the welfare of a child.

The alleged incident happened on Sept. 14 inside a classroom in P.S. 200 on Benson Avenue in Bath Beach.

Police say Abdelrahim, who works as a paraprofessional at the school, was seen by co-workers who reported he was holding a child's head on his lap and appeared to be sexually aroused. 

Abdelrahim was arrested at the school, police say. He does not have any prior arrests. 

The boy was not injured during the incident.   

The city's Department of Education has since fired Abdelrahim, saying he will never work again in city schools.