Following numerous reports on social media about a 'strong police presence' near Angmering Railway station, Sussex Police revealed officers were called to an incident in Station Road at 6.25pm.
A spokesman said: "We were called to a school in Station Road, where three masked youths were seen on the roof, throwing stones at people.
"One was also seen to be tying to force open a skylight.
"The youths ran off [upon the police's arrival] and we stopped some shortly after, but they weren't the ones involved.
"The police presence was treated as a break-in, in progress but this turned out not to be the case.
"We liaised with the school caretaker. There was no damage caused and there was no trace."