Dorset Police said three passengers and the driver of a double-decker bus have been treated for "minor injuries"
The bus, registered to Plymouth, was heading to Kingston Maurward College in Dorchester, police said.
Police, ambulance and fire crews were called to the A350 this morning after reports that a school bus had overturned in a field.
Three people and the driver were treated for minor injuries, and all those on board were moved to safety while they wait for replacement transport.
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A largely fine day with sunny spells, although there is a chance of the odd shower in the afternoon.