Head teachers and their staff have taken to Twitter to highlight what may have to be axed in schools in England because of budget cuts.
There have been more than 27,000 tweets using the hashtag #whatwouldyoucut since the campaign against the cuts started on Sunday.
The government insists school investment is at a record £40bn.
But the Association of School and College Leaders said this was only because pupil numbers are rising.
It argued that head teachers are having to make tough decisions about which services to cut.
The tweets included photographs of science experiments, school trips, sporting activities and performing arts events.
Lostock Hall Primary School in Stockport suggested its library could be a candidate for the chop.
The idea for #whatwouldyoucut came from a group head teachers in Cheshire East – one of the country’s worst-funded areas in the country, which is set to loose out even more under the government’s planned new funding formula.
ASCL interim general secretary Malcolm Trobe said: “The survey shows the impossible choices school leaders are having to make.
“Reduced budgets means fewer staff and, with fewer staff, class sizes have to increase. Schools cannot sustain the level of support they provide to pupils, or the range of subject options and enrichment activities.”
Schools have been writing to parents warning them of tricky budget decisions to come, while groups of heads have been lobbying the Education Secretary setting out their difficulties.
The Department for Education said it was protecting per pupil funding so where pupil numbers rise, the amount of money schools receive will increase.
“The government has protected the core schools budget in real terms since 2010, but the system for distributing that funding across the country is unfair, opaque and outdated.”
This was why it was bringing forward a new national funding formula, under which half of England’s schools will receive a cash boost in 2018-19, it added.
One tweet suggested the length of school day could be shortened.
The Twitter campaign comes in the run-up to the Budget on Wednesday.
Currently, the level of funding per pupil is frozen and is expected to fall by 6.5% in real terms between 2015-16 and 2019-20 because of rising costs.
These funding pressures include increases to employer contributions to National Insurance and pensions, nationally agreed pay awards, and the new Apprenticeship Levy which comes into force next month and which many schools will have to pay.
Kevin Seaward, an Irish marathon runner and assistant head teacher, was part of the Ireland Olympics team in 2016.