A plan to create a new school in Chipping Barnet for pupils with special educational needs has been approved by councillors.

The Windmill School in Moxon Street will be a free school for pupils aged between five and 18 years with a diagnosed autistic spectrum disorder and an education, health and care plan (EHCP).

Due to open in September next year with an initial capacity of 23 pupils, rising to 90 by 2026, it will be the only autism-specific maintained school in Barnet.

The plans involve the part-demolition of the existing building, which is currently used for storage and distribution, and several alterations and extensions to create the school. A multi-use games area and sensory garden will be created on the roof of the building.

There is a growing need in Barnet for special educational needs and disabilities places at both primary and secondary level, particularly for those with autism.

The plans were presented to Barnet Council’s strategic planning committee on Wednesday. During a prior public consultation on the scheme, the council received ten objections and five letters of support.

During the meeting, Robin Bishop, chair of the Barnet Society’s planning and environment committee, spoke against the proposals. He said that the society “would love to have a school of this kind in Barnet” but the committee was “deeply concerned” about this particular one.

Robin said the society’s principal objection was that the rooftop playground would be “only about 20% of the DfE’s [Department for Education] minimum recommendation for a school of this size”.

He raised concerns that the school would not be able to provide enough play equipment for different age groups or have the resources to allow pupils to access nearby green spaces.

But Ian Kingham, academy development director at the Barnet Special Education Trust, urged the committee to support the plans.

He told councillors the school would provide “an autism-specific, predictable and purposeful learning environment in which pupils can thrive, and where they will have the best chance of achieving academic success and personal growth”.

Responding to the objection, Ian said the school planned to limit the overall numbers in the play area by allowing different groups of pupils to use it at different times, adding that the school would also make use of local open spaces such as Monken Hadley Common.

Under questioning from councillors, he said the site was the “best viable option” for the school following an extensive search for a suitable location.

Stephen Sowerby, a Conservative committee member, said he was “overjoyed” that a use had finally been found for the site. He said there had previously been “at least three planning consents” for flats at the site, but none of these had been built.

The committee voted unanimously to approve the plans.