Two students were hospitalised following a road accident involving a school bus and a van on the Marlton Road in Co Wicklow.
Gardai were called to the scene near the junction between the Beehive Inn and Wicklow town at 8.10am as the bus was travelling to Wicklow Post Primary Centre.
The impact caused the front window of the 52-seater bus that was carrying 15 secondary school students to be pushed in.
According to a statement from the Garda Press Office, two children were treated at the scene just off the N11 for very minor injuries.
Vice-principal of the Dominican College in Wicklow town, Neal Martin, confirmed that two students who were on the bus were taken to hospital.
Ambulances, a number of fire brigade units and gardaí from Wicklow town attended the scene.
The crash resulted in the closure of one of the lanes on the road for a time.
"Bus Éireann are aware of an incident which took place at 8.10 this morning while travelling to Wicklow Post Primary Centre," Bus Éireann said in a statement.
"There were 15 pupils on-board at the time, emergency services attended the scene and four pupils were brought to hospital for further medical attention."
An investigation has been launched into the crash.
Meanwhile, a Dublin bus driver suffered a heart attack while on duty during rush-hour traffic in the city centre.
The incident resulted in emergency services closing O'Connell Bridge while the driver received emergency treatment.
Gardai announced on its official Twitter page that O'Connell Bridge had been closed off from South Quay to North Quay due to an “ongoing incident.”
Dublin Bus later confirmed that an incident took place on a Route 16 bus on O'Connell Bridge during the morning.
It stated that the bridge was opened to traffic after the driver was transferred to hospital by the emergency services.
Dublin Bus said it would not be making any further comment.