Walk into one of England’s schools with an above-average proportion of pupils with special educational needs and disabilities, and you may see some of the strongest examples of inclusive practice: experienced staff, thoughtful routines and a culture where pupils feel genuinely included.

But there is a harder truth beneath this success. Many of these schools are carrying a disproportionate share of responsibility on an increasingly unsustainable basis, as rising levels and complexity of need outpace available resources.

Our latest NFER research, drawing on national data, a survey of 800 Sendcos and school leaders, and in-depth school case studies, suggests this is not a coincidence.

It reflects a set of powerful push-and-pull factors that are concentrating pupils with SEND into a subset of mainstream schools, with significant consequences for children, families and the system.

The pull: schools that make inclusion work

Parents are not choosing schools randomly.

Families repeatedly told us that they actively sought out schools known for inclusion: schools where staff “understand children with special needs”, where flexibility is embedded and where pupils are treated as individuals.

As one parent put it: “It’s in their bones…you can feel the ethos.”

Once a school develops a reputation for inclusion, word spreads quickly through parents, professionals and local authorities. Demand rises, drawing in more pupils with SEND.

Specialist provision, such as SEN units or resourced provision, can intensify this. These schools become seen as safe and reliable options when others cannot meet need.

The push: a system under strain

But attraction is only part of the story. Many pupils are not simply choosing these schools - they are being steered towards them.

Across the system, capacity is stretched. There are too few specialist places; education, health and care plan (EHCP) processes are slow; and decisions are often made under pressure. Inclusive mainstream schools become the default option.

School leaders said that local authorities frequently asked them to take pupils despite them making it clear they could not meet need: “The children are still coming.”

At the same time, some schools are wary of developing a reputation for taking pupils with SEND because of concerns about funding, staffing and accountability pressures. That further narrows the pool of schools seen as “available”, reinforcing the cycle.

Why pupils stay - and why concentration grows

Once pupils with SEND are in these high-SEND schools, they are less likely to move than similar pupils elsewhere.

This may be because staff develop expertise, pupils feel a sense of belonging and families feel they have finally found the right fit.

But it also means that concentration deepens over time, as more pupils with SEND arrive and fewer leave.

Centres of expertise

High-SEND schools often become centres of expertise, with strong inclusive cultures and confident staff.

But many leaders of these schools describe mounting pressure on staffing, budgets and leadership time, alongside a growing reliance on goodwill to sustain provision.

There are also wider equity concerns. Not all schools are sharing responsibility equally, and not all families have the same ability to access the most inclusive schools.

If the government is serious about the ambitions set out in its White Paper Every Child Achieving and Thriving, it cannot rely on a minority of schools to “make it work”.

What needs to change

Three shifts are needed.

First, pupils with SEND need to be distributed more evenly across local systems, supported by stronger place planning and monitoring.

Second, accountability measures must better reflect inclusion. As long as schools feel penalised for admitting higher-need pupils, the incentives driving concentration will remain.

Third, funding must better follow need. Where need clusters, resources must, too.

Parents will always seek the best for their children, and most schools will always want to do the right thing. But unless every school is supported - and expected - to play its part, the system will continue relying on the same schools to carry the load.

That is not a sustainable model for inclusion

Matt Walker is senior research manager at NFER (National Foundation for Educational Research)