A special needs school has cut the day by 30 minutes because of education funding cuts.
Selly Oak Trust School in Birmingham has written to parents telling them that the school day will be shortened from September as a money-saving exercise because of the cuts to education funding.
While it is understood to be the first school to take such drastic action because of the cuts, others have been writing to parents asking for regular cash contributions or money for books.
However, there are fears more may now follow.
In the letter, head teacher Chris Field said the school had already made "significant changes" but they had not been sufficient.
He wrote: "The school leadership team and governors have not taken this decision lightly. We also understand that this will have an impact on families.
"However, we believe that this change will ensure that we meet the savings demanded of us, without affecting the quality of our students' education in a safe environment."
Parent Vanessa Kellett told Sky News: "It is sad really you think about the next generation. I have got a younger daughter and you have to ask what's next?"
Michelle Mansell, who has two children at the school, blamed the Government for the financial difficulties.
"What's next? Starting at ten o'clock and finishing at one o'clock? What then is the point of having an education?"
Labour MP for Birmingham Selly Oak Steve McCabe said 35 of the 37 schools in his constituency were facing cuts.
He said: "The problem is that once you make all those cut on the school minibus, and cuts to books, your only option is to shorten the school day or sack staff."
It comes after a warning by head teachers last month that schools could start closing early two days a week or cut A-levels in subjects taken by only a few pupils to save on teaching costs.
Malcolm Trobe, interim general secretary of the Association of School and College Leaders, said he had heard a number of head teachers have been thinking about reducing the number of lessons provided each week.
He said: "For example, if you would normally run 25, one-hour lessons a week, you may go down to 23, with a shorter Wednesday and a shorter Friday."
He explained that many schools felt the cuts would have to come from the staffing budget.
He added: "Essentially they haven't got enough teaching time to keep the whole whack going."
Head teachers across the country are facing the double blow of a freeze in the schools budget, which represents a 6.5% cut in real terms by 2020, as well as changes in the education funding formula.
The funding formula move looks to redress the balance, which has seen some London schools getting twice as much cash as schools in other parts of the country.
The proposals would see 11,000 schools better off but 9,000 losing out.
A study by the Institute for Fiscal Studies has found the changes would see 1,000 schools facing a 7% cut by 2020.
Mrs May faces a backbench revolt over the issue - at least one in five Conservative MPs have constituencies adversely affected by the changes.