According to the prosecutor, the boy held the girl, hugged her and also pawed at her.
The incident is said to have taken place in early May last year when the girl was 14 years old.
After the incident, the girl is said to have turned to the school staff and told them about the sexual harassment, after which the staff produced a surveillance film which is now part of the prosecutor's evidence.
During the trial, interrogation will take place with the suspect boy, the affected girl and a witness to the incident.
The witness must, among other things, corroborate the prosecutor's crime allegation that the suspected boy knew how old the girl was when the crime was committed.
According to the prosecutor, there is uncertainty about the boy's attitude to the suspected crime.