Schools in England are facing their toughest spending squeeze in two decades, jeopardising standards in the classroom, MPs have warned.
The Commons Public Accounts Committee said class sizes would rise and some subjects would be dropped as schools increasingly relied on unqualified staff in a struggle to make ends meet.
In a scathing report, the committee accused ministers of failing to learn the lessons of the NHS where "unrealistic" targets and "ineffective" leadership had caused long-term damage to the service's finances.
Committee chairman Meg Hillier said there appeared to be a "collective delusion" within the Government at the scope for savings across public services.
Rising costs, such as pay and pensions and employers' National Insurance contributions, mean schools will have to find efficiency savings of £3 billion by 2019-20 - 8% of the total budget - in the sharpest reduction in their spending power since the mid-1990s.
The Department for Education (DfE) has said that it expects £1.7 billion to come from using staff more efficiently with the rest through better procurement.
However, the committee said ministers had failed to put in place arrangements to monitor the impact of the cutbacks on the quality of education pupils were receiving.
The DfE argued existing measures, such as Ofsted inspections and key stage tests, would show whether educational outcomes were being maintained.
But the committee said these indicators were "timed-lagged" and the full impact of the cuts may not become apparent until 2021 when the new GCSE results come through - "too late" for children at school now.
"The department does not seem to understand the pressures that schools are already under," the committee said.
"To reduce staff costs, schools are likely to increase teachers' contact time and class sizes, rely more on unqualified staff and staff teaching outside of their specialism, and require head teachers and other senior staff to do more teaching.
"The head teachers who gave evidence told us that they plan to make savings by, among other things, dropping subjects and scaling back on school trips to avoid the cost of teaching cover.
"The actions schools take are likely to increase teachers' workload, with implications for recruitment and retention, and put at risk the quality of education."
The committee said that while its previous reports had highlighted the "counter-productive" effect "over-ambitious" efficiency targets had had on the NHS, the DfE appeared to be unaware of the problem.
"We are concerned that the department does not seem to recognise the similarities and the opportunity to learn lessons," it said.
Ms Hillier said the future education of pupils was at risk if the Government failed to act on the report's warning.
"It sets out more evidence of what increasingly appears to be a collective delusion in Government about the scope for further efficiency savings in public services," she said.
"Grand plans drawn up in Whitehall are dangerous if they are implemented without regard to real-world consequences and we will expect to see measures to address our concerns as a matter of urgency."
A Department for Education spokesman said: "We will study the report's recommendations and respond in due course.
"Standards in our schools are rising with 1.8 million more pupils being taught in good or outstanding schools than in August 2010.
"We have protected the core schools budget in real terms since 2010, with school funding at its highest level on record at more than £40bn in 2016-17 and that is set to rise, as pupil numbers rise over the next two years, to £42 billion by 2019-20.
"These protections, and the wider investment in the school system, mean that spending per pupil will be over 50% higher in real terms in 2020 than it was in 2000, as set out by the independent Institute for Fiscal Studies.
"We recognise that schools are facing cost pressures, and we will continue to provide support to help them use their funding in the most cost effective ways, so that every pound of the investment we make in education has the greatest impact.
"This includes improving the way they buy goods and services, while our recently published school buying strategy is designed to help schools save over £1bn a year by 2019-20 on non-staff spend."