The A10 has re-opened in both directions at Hilgay, near Downham Market, after being closed for more than six hours after a coach crash.
The children were among a party from the William Westley Primary School at Whittlesford, near Cambridge, who were on their way to the seaside.
They were travelling in a convoy of three coaches, owned by Royston-based Richmond's Coaches, when the accident happened.
A spokesman for the Confederation for Passenger Transport, the trade body for coach operators, said: 'We don't know what happened but one of the coaches left the road and ended up in a ditch.
'The drivers from the following vehicles were able to assist in safely evacuating passengers from the coach and we believe there are no reported injuries.
'A replacement coach was sent to collect passengers and they're all returning to school.'
He added the coach involved in the crash was a modern vehicle, fitted with lap belts.
A spokesman for Cambridgeshire County Council, speaking on behalf of the school, said: 'The bus which ended up in the ditch was one of three travelling in convoy so the children simply got on to the other two buses and are being taken back to the school. All of them are unhurt.
'Arrangements will be made to inform parents of the next steps but it's unclear at the moment whether children will be sent home.'
Police said the single vehicle accident happened just before 11am.
Emergency services including four fire engines attended the scene of the collision, between Dent's Farm Shop and the Ely Road junction.
A police spokesman said: 'It has been confirmed that the coach contained 42 primary school children, five members of staff and one parent helper from the Cambridge area and the driver.
'The children and staff members suffered only minor injuries as a result of the collision and were able to leave the coach immediately.
'A number of them received treatment for shock at the scene but did not require hospital treatment. The driver had to be cut free from the coach and has been taken to hospital for treatment for suspected back injuries.'
The coach has now been recovered and the road reopened.
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