Half of sixth forms in schools and colleges have been forced to drop A-levels in modern languages as a result of “totally inadequate” funding of post-16 education, according to research.

French, Spanish and German have been hardest hit – 57% of sixth form leaders who took part in a survey said German courses had been axed, 38% have dropped Spanish, 35% had ditched French and 15%, Italian.

The poll by the Sixth Form Colleges Association comes as concerns rise about dwindling language skills in schools, but school and college leaders say funding cuts and cost increases in post-16 provision make it impossible to put on courses for small numbers of students.

Highly rated courses in science, technology, engineering and maths (Stem) are also suffering. More than a third (38%) of those surveyed have dropped Stem courses for the same reasons. Three quarters (78%) have cut student support services or extra-curricular activities and eight out of 10 (81%) institutions have bigger classes.

Students are getting fewer teaching hours, with 46% of school and college leaders admitting they have cut delivery hours;68% have moved from a standard four-subject offer to three A-levels.

The SFCA says the survey, which is based on responses from a sample of 271 schools and colleges teaching 26% of the cohort of 16- to 18-year-olds, exposes the damaging impact of funding cuts on sixth form education, which is one of the hardest hit areas in education.

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Research from the Institute for Fiscal Studies last year found that in real terms government spending per student in school sixth forms fell by more than 20% between 2010-11 and 2017-18. Campaigners for fairer funding are calling for an increase in the annual funding rate from £4,000 per student to at least £4,760.

Bill Watkin, the SFCA chief executive, said: “Today’s report makes it absolutely clear that the government must increase the funding rate for sixth form students in this year’s spending review.

“If we are to keep key subjects on the timetable, offer a wide range of extra-curricular experiences, and provide the essential support activities that our young people need and deserve, the government must raise the rate to at least £4,760 per student, per year.”

Geoff Barton, the general secretary of the Association of School and College Leaders, added: “Government funding for 16 to 18 education is set at a level which is totally inadequate. The grim reality is that this policy decision is restricting the options and support available to young people in the state sector and it is impeding efforts to improve social mobility.”

The Department for Education said: “We have protected the base rate of funding for 16- to 19-year-olds until 2020. We will also be providing £500m every year, from 2020 to support the delivery of the new gold standard T levels – which some sixth form colleges will be offering. However, we recognise that the financial position for sixth form colleges is challenging and are looking carefully at the needs of all colleges in the run-up to the next spending review.”