School closures are inevitable over the next three years as lawmakers continue to make “secretive, politically motivated” financial decisions that risk progress in education, MSPs were warned this week.

Unions and parents’ groups criticised Scottish councils for failing to provide details of budgets for reasons of “confidentiality”, and publishing information that “someone with a maths degree would struggle to understand”.

The groups called for comprehensive figures to allay concerns about variations in school spending between councils. They voiced fears that some local authorities could be wasting vital money on “fluffy” items such as “certain types of wheelie bins”.

Unions, parent groups and youth groups also urged councils to discuss budgets openly and early with parents and pupils, instead of making decisions behind closed doors.

The warnings came during the latest Education and Culture Committee debate on the draft Scottish budget for 2015-16, which is expected to hit education hard after services were largely spared in previous cutbacks.

Eileen Prior, the executive director of the Scottish Parent Teacher Council, told the committee that when she tried to find out how school funding decisions were made by councils she was told (by an unnamed education official) that “only two people know that and one of them is dead”.

She said it was “unacceptable” that school budget decisions were conducted without transparency.

“There is such disparity between local authorities; rurality [alone] does not explain it. I’d like to see the figures to understand why they are as they are,” she said.

Parents were “patronised” by councils, who said that they didn’t need to understand the “really complicated” sums and instead gave them a “menu of services to cut” rather than involving them in making decisions, she added.

Iain Ellis, chairman of the National Parent Forum of Scotland, said that even a maths graduate would struggle to make sense of council budget documents.

Referring to the upcoming elections, he warned: “Suddenly money becomes available for policies. They [politicians] need to stop trying to pull the wool over our eyes and fund policies properly. In the next three years there will be serious cuts to education and the only way to make serious cuts is through school closures and staff reductions. Curriculum for Excellence could be excellent but it could be lost.”

Jane Peckham, organiser of the NASUWT Scotland teaching union, said she felt that some local government money was wasted on “fluffy” costs, such as purchasing a particular kind of wheelie bin or sending out council information leaflets.

She was “concerned” to hear that councils did not share budget information with parents, and “doubted” that councils were sharing details of successful savings mechanisms.

Meanwhile, unions and parents’ groups also questioned the need to retain all of Scotland’s 32 councils and warned that authorities must do much more to share services in light of swingeing cuts, even though that would inevitably lead to redundancies and shutdowns.

Mr Ellis challenged MSPs to consider whether continuing to leave education services in the remit of Scottish councils was the “best way”. “We seem to be rationing everything else, like Police Scotland. Should we do away with local authorities altogether too?” he asked.

Speaking to TESS after the committee meeting, he said he did not believe that “radical” change was the answer, but added: “Glasgow is a huge authority. You could put four or five smaller councils together and they would still be smaller than Glasgow. We have to look at more shared services. And if you have two small primaries next to each other, it is not efficient.”

Echoing Mr Ellis’s views, EIS general secretary Larry Flanagan said: “Do we really need 32 education directors?”

Schools had to work together more and accept that worthwhile policies like the 1+2 language drive had “no chance” of being implemented successfully under current and expected future funding, he added.

Local authorities body Cosla, which will give evidence to the committee next week, said that education was the largest service provided by local government and therefore the “biggest financial challenge”.

A spokesman said: “Balancing budgets is not a simple task so councils will try to engage the public as best possible on the future of education services. The reality, though, is that.all councils face difficult and potentially unpopular decisions on education and other local government services.”

A government spokesperson said: “The Scottish government fully supports transparency in decision-making that is accessible to members of the public. It is the responsibility of individual local authorities to manage their budgets and to allocate the financial resources available to them on the basis of local needs and priorities, having first fulfilled their statutory obligations and the jointly agreed set of national and local priorities.”