Department for Education figures show 18 primary schools were at or over capacity in Barnsley in the 2021/22 academic year.
The figures show the most crowded primary school in Barnsley last year was Cudworth’s Birkwood Primary School.
The school had 314 students on roll and 280 places meaning it was over capacity by 12 per cent.
The most crowded secondary school in the area was Penistone Grammar School which had 1,818 pupils and 1,820 places last year.
It was at 100 per cent capacity.
Barnsley Council say work has already - or is currently - been completed to help address the situation.
A spokesperson said: “We carefully monitor school places and forecast demand to make sure that all children have a local school place, using birth data, recent trends, and housing growth.
”Work to increase capacity at Birkwood Primary School started in March 2022 to increase the published admission number from 40 to 60 places.
“The work is due to be finished in the next academic year and this will have increased the school’s capacity to 420 school places.
“The first increased intake of 60 reception pupils were admitted in September 2022 after the first phase of work was complete.
”Penistone Grammar School is a popular school and work was completed in 2020 to increase capacity by 50 pupils per year from 270 to 320 places.”