A Sydney student from the same high school attended by a teenage gunman who shot a police accountant dead outside Parramatta's Police Headquarters has reportedly been arrested.

The Arthur Phillip High School student was handcuffed and had his belongings emptied on the footpath while on his way to school, ABC reported on Tuesday.

The NSW Department of Education told AAP it was waiting for details from police on the matter.

The ABC cited the boy as saying police did not like him videoing them on his mobile phone.

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The teenager was arrested just after 8.30am after he allegedly threatened and intimidated police who were speaking to the boy about posts on social media.

The teen has been taken to Parramatta police station.

NSW school students returned to classrooms on Tuesday after the two-week school holiday.

The NSW Department of Education said counselling services will be offered to students and staff at Arthur Phillip High School after Friday's shooting.

- AAP