There is "lack of coherence and coordination" in special needs provision at a local level, with the challenges underpinned by a "chronic lack of funding", Ofsted has warned.
In its annual report for 2018-19, the inspectorate says that area leaders have a "weak understanding" of the lived experiences of children with special educational needs and disabilities (SEND), with poor joint commissioning contributing to "ineffective" services.
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And local leaders across education, health and care "do not always see themselves as collectively accountable" for SEND provision, the watchdog adds.
"The local offer is inaccessible or difficult to navigate," its report says.
"Communication between education, health and care professionals, and between professionals and families, is poor.
"Families do not know where to get the help and support that their children need."
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The inspectorate adds that "fractures" exist in assessment and planning", meaning that the system is not working well to "make the best decisions and achieve the best outcomes for children and young people".
"Too many EHC [education, health and care] plans are not finalised within the 20-week timescale, and the quality of plans is too variable," the report says.
During the 2018-19 academic year, Ofsted and the Care Quality Commission (CQC) jointly completed 33 inspections of SEND services.
Nearly two-thirds (21) of those areas inspected required a written statement of action (WSoA).
Chris Keates, acting general secretary of the NASUWT teaching union, said Ofsted was right to highlight that pupils with SEND were being let down.
“In particular, Ofsted is right to highlight that in too many cases across the country, SEND pupils are being let down by failures in joint working arrangements between schools, local authorities, health and care services," she said.
“Too many areas suffer from fragmented and poorly co-ordinated services. In such cases, it is often hard-pressed teachers and school leaders who are left to try to fill in the gaps left by the absence of external support."