South Wales Fire and Rescue Service said no one was injured after the fire broke out at St Athan Primary School.
Council chief executive Rob Thomas has praised school staff as well as officers from South Wales Fire and Rescue Service (SWFRS) for their response.
The fire was contained within a small block of classrooms and was prevented from spreading to the main part of the school, according to the fire service.
He said "the only thing that mattered was that no one was hurt" and paid tribute to the "professionalism" of staff and the "swift attendance" of the fire service.
A fire at a school in the Vale of Glamorgan forced around 240 staff, pupils and contractors to be evacuated.
