Calderdale has 14 schools which are full or overcapacity, new figures reveal.
The National Education Union has accused the Government of “inadequate planning” for the increase in pupil numbers, and argued local authorities should be allowed to open new schools.
Department for Education data shows there were 14 primary schools in Calderdale either at full capacity or overcrowded last year. No secondary schools were overcapacity.
That leaves Calderdale’s schools overcapacity by 72 pupils, which means even more are learning in crowded classrooms.
The same number of schools were full or overcapacity in 2016-17.
Across Yorkshire and the Humber, 456 schools were full or overcrowded, with almost 5,000 fewer spaces than pupils.
Andrew Morris, assistant general secretary of the NEU said this “is an unacceptable state of affairs”.
“Our children and young people only get one chance for an education,” he explained.
“This is the result of the Government’s inadequate planning for the increase in pupil numbers and its insistence that local authorities should not be permitted to open new schools.
“This lack of foresight, combined with the year-on-year funding squeeze, has resulted in the highest number of secondary school students in classes of more than 30 since 1982.
“Running schools in an incoherent fashion on a shoestring budget is not good enough.”
Across England, the increase in pupils by 2020-21 is estimated to be almost three times the number of additional planned school places, according to the DfE.
In Calderdale, 1,451 additional pupils will need to fit into 501 places planned by the local authority, which could make schools even more overcrowded.
The data does not include free schools.
Speaking about the figures, the Education Secretary, Damian Hinds, said: “Children only get one chance at an education and they deserve the best, wherever they live and whatever their background.
“That’s why this Government is undertaking the biggest expansion in school places in two generations – and the statistics show we are well on track to create 1 million places this decade.
“With standards rising in our schools this will mean that more families have the choice of a good school place.”
A DfE spokeswoman added that the number of pupils overcapacity has fallen from 97,000 in 2010 to 50,000 in 2018.