The accused, identified as Rajkumar, is married and has a five-year-old son. He has a private coaching centre at his residence, police said today.
The incident came to light yesterday when parents of both the girls, who used to take coaching classes from Rajkumar, approached the police and two separate cases were registered.
"In both cases, the accused has been booked under relevant sections of the IPC and POCSO Act. He was arrested immediately," DCP (northwest) Vijay Singh said.
When the neighbour enquired whether their daughter knew anything about the incident, the seven-year-old girl broke down and said that she too was a victim.
The accused had been allegedly sexually assaulting the two for around the past 15 days, said an official.
Parents of both the girls approached the police together. The police are now verifying whether the accused had assaulted other students too, the official added.