Police on Tuesday morning have arrested and charged a student on his way to Arthur Phillip High School, the same school attended by the teen gunman behind last week's fatal shooting in Parramatta.

The student claimed that he was arrested because he was using his mobile phone to film officers who were positioned outside the school, as classes returned for the first time since Friday afternoon's shooting outside the NSW Police headquarters.

However, police said that officers had spoken to the teenager at about 8.30am in relation to alleged posts he had made on social media.