Consultant firm ISOS are set to go into schools and work with leaders over the next three months to come up with a plan to tackle overspending for the high needs block in the education budget.
The high needs block provides funding for children with an education health and care plan (EHCP) in place, who need extra support by the schooling system.
There are currently 3,400 children with an EHCP, 23 per cent more than estimated when the budget was set.
The high needs block in Wiltshire is overspent by £4.5m.
If the cash cannot be paid back within three years, Wiltshire Council could be faced with paying the deficit out of funding reserves.
Ben Bryant of ISOS said: “There are no easy answers and no guarantees.
“We have told the Department for Education there’s a huge funding gap.
“Local areas are massively propping up the block.
“Your overspend is not so big that it feels pointless trying to get out because the cycle of placement breakdown and crisis points becomes so vicious, like in some other parts of the country.”
Schools Forum, made up of school and early years leaders, recently agreed to transfer one per cent of the 2019 Dedicated Schools Grant £351m allocation to partly fill the high needs funding gap.
Its chair Neil Baker said: “Having a £4.5m overspend does not feel like a trivial overspend.
“Any solution has to take into account affordability.
“It could be the case that our children in Wiltshire are being well provided, which is why we are overspending, because we see their needs as important.
“But when schools get the funding directly from the National Funding Formula, that pot will be £4.5m short and then it will be the resources for special needs children that will have to be cut.
“This review is will placed and we need those difficult questions to be asked.”
Wiltshire Council has ringfenced £1.3m from its £12m reserves to make up the shortfall, however it is lobbying the government to increase funding in this area to avoid using the reserves.
In December the secretary of state provided £250m of funding to cover extra support for children with special needs.
Wiltshire was given £1.128m from the funding pot.