First Hampshire and Dorset say: "We can confirm that there has been an incident this morning involving one of our buses, travelling from Poole to Kingston Maurward College.
"There were a number of students on board the vehicle at the time, five of whom are thought to have sustained injuries.
"The driver of the bus has not been injured but he is being treated for shock. The emergency services attended the scene of the incident and those injured have been taken to hospital for treatment.
"The exact cause of the incident is not yet known but it will be thoroughly investigated.
"Our team are at the scene and they will work closely with the relevant authorities to determine exactly what has happened.
"Our thoughts, however, are currently with those who have sustained injuries as a result of this incident; we wish them all a full and speedy recovery."