Disabled children and their families have taken to the streets today to demand action on "the national crisis" in special needs funding.
Send National Crisis campaigners delivered a 13,000-signature petition to Downing Street ahead of a rally in Parliament Square.
They say special needs funding is failing to keep pace with demand.
Ministers say they are increasing the cash available.
The organisers say rallies in 28 towns and cities, from Leeds and Liverpool to Reading and Rhyl, are part of the first national action of its kind.
They point to reductions in school and college funding with "vital teaching assistant support being cut".
Also, they say, funding pressures on councils have led to the widespread closure of children's centres "which provide essential support for disadvantaged and disabled children".
They add: "As a result, more disabled children are out of school, or being illegally excluded or off-rolled, and more families are having to fight to get the right provision."
Nadia Turki, Send National Crisis co-founder, said: "We can no longer remain silent when our children are suffering for want of adequate government funding."
Ms Turki says the organisation is demanding better regulatory controls to ensure that funding for special needs and disabilities is ring-fenced and delivered "precisely where it is most needed".
In April, analysis by the National Education Union (NEU) found that central government funding had failed to keep up with demand for special needs education to the tune of £1.2bn since 2015.
"This is clearly a crisis, with pupils and parents bearing the brunt of real-terms funding cuts and the wholly inadequate planning by government," said NEU joint general secretary Kevin Courtney.
Paul Whiteman, general secretary of the head teachers' union NAHT, added: "We urgently need the government to recognise the true scale of the problem and release more money from the Treasury, both for schools and for health and social care services."
The government reformed special education provision in England back in 2014, replacing special needs statements with Education, Health and Care plans (EHCs), aiming to deliver a "simpler and more joined up system", from birth to age 25.
But five years on, parents and carers say the system is not working and last year, Ofsted described the failure to deliver support for thousands of children in England with diagnosed special educational needs as "a national scandal".
The report highlighted the cases in 2018 of 2,060 children, whose needs were set out in EHC plans, but who were receiving no support.
This figure was even higher in 2017 at more than 4,000.
The government says it is listening.
Children and Families Minister Nadhim Zahawi said: "Our ambition is for every child, no matter the challenges they face, to have access to a world-class education that sets them up for life.
"Funding for the high-needs budget is a priority for this government and we know that councils and schools are facing pressures. That's why in December we provided an extra £250m up to 2020 to help manage these costs.
"This takes the total amount that we have allocated for high-needs funding to £6.3bn this year, compared to £5bn in 2013.
"At the same time, the education secretary has been clear that we are working closely with the sector as we approach the spending review and we have launched a call for evidence to make sure the funding system is getting money to the right places at the right time.
"We are revising the Send code of practice to improve ways to identify and meet special educational needs."