A joint inspection by Ofsted and the Care Quality Commission found that pupils with SEND are not doing well enough in mainstream education in the county, particularly in reading, writing and maths in primary school. They are also struggling across a range of subjects in secondary school.
The high exclusion rate of pupils with SEND in Northumberland is another concern raised. The insperction, which took place in October, also found that leaders across Northumberland County Council and Northumberland Clinical Commissioning Group (CCG) are not working well together to commission, plan and provide support to improve this group of children's lives.
Leaders were found to lack understanding about what they need to do to improve support for children and their families. They were also found to be failing to evaluate whether existing provision is working well.
"Children and young people with SEND do not do well enough in mainstream primary and secondary schools," states a letter outlining the findings of the inspection.
"They do not make strong enough progress in reading, writing and mathematics in key stage 2 or in a wider range of subjects in key stage 4. Too many children and young people with SEND are excluded from schools in Northumberland."
"Leaders do not have a sophisticated enough understanding of what is working well and what could be better for children and young people with SEND and their families.
"Importantly, leaders are not currently able to measure or evaluate the impact of their work on the experience of children, young people and families or the outcomes they achieve."
Inspectors also warned that co-production, whereby children, families and professionals work together to plan support, is "patchy". While some families were found to have "strong and influential voices" others "do not feel heard", inspectors found.
Identification and assessment of SEND is also variable, but inspectors noted that there "has been a determined drive" to improve in this area.
The inspectorates also praised the dedication of frontline staff, who "work hard and are making a valued difference to children and young people with SEND and their families".
The county council and CCG have been asked to write to the inspectorates detailing how they will improve support.
"We welcome the findings of the Ofsted and CQC report which outlines areas of strength and good practice within some services, as well as other areas where there is still work to do, which we acknowledge," a joint statement from the county council, CCG as well as Northumbria Healthcare NHS Foundation Trust, said.
"Across the whole UK though, demand for services is increasing and Northumberland faces similar challenges to many other local authority areas. We're determined to address these, and have firm plans in place across all service areas to expedite improvements as quickly as possible."
This month Ofsted said that almost half (30) of the 68 local areas inspected for SEND provision in 2017/18 were asked to provide a written statement of action due to concerns raised.
Meanwhile, Ofsted and CQC also visited SEND services in Milton Keynes in October. A letter to Milton Keynes Council and CCG praises the quality of support in the area, in particular their analysis of evaluation to ensure services can continue to improve.
Among areas singled out for praise was support for young offenders with SEND. Within the youth offending team, speech and language therapists carry out assessments as soon as the young person makes contact, inspectors found.
"As a result, many young people are enjoying a successful reintegration into education," states the inspectorate's letter to the council and CCG.
"The positive impact of this cohesive approach can be seen in the impressively low reoffending rates in Milton Keynes, which are the second lowest in the country."
The area's SEND independent advice service (IAS) was also praised for providing parents with a wide range of support, advice and training.