Ministers’ grammar school plans have been dealt two blows, with lawyers arguing that a key plank of the scheme is “not lawful” and lack of parental support scuppering the first proposal for a comprehensive to convert.

The NUT teaching union has received legal advice stating that the government’s plans to expand selection via multi-academy trusts (MATs) would break the law, TES can reveal.

The disclosure comes after it emerged that the first non-selective secondary to register its interest in becoming a grammar since the government announced its plans - Meopham School in Kent - had decided against it after parents were split 50/50 “for” and “against”.

If the NUT’s legal claim is correct, it could pose a problem for the government’s grammar school agenda, because ministers would have to rely on pushing through new legislation in the teeth of widespread parliamentary opposition.

‘Court action is an option’

In September, the government published its grammar school Green Paper Schools that Work for Everyone, which included a proposal to “encourage multi-academy trusts to select within their trust”.

“We will make clear that multi-academy trusts …[can] establish a single centre in which to educate their ‘most able’ pupils,” the paper states.

It says that this form of selection is permissible because pupils are identified as “most able” after being admitted to school “through a non-selective admissions process”.

However, the NUT said it had received legal advice that this was incorrect.

Kevin Courtney, the union’s general secretary, outlined its legal objections in a letter sent to education secretary Justine Greening last week, shared exclusively with TES.

“I am advised that selection within academy trusts in the manner described in the Green Paper - whether it is read as referring to admission to a specific school within the trust or to a ‘centre of excellence’ which is not itself a school - is not lawful,” Mr Courtney writes.

According to the NUT’s advice, legislation passed in 1998 is the only method for selection, and any attempt by MATs to move children between different schools or centres based on ability would be against the law.

However, one commentator said the legal situation regarding MATs was less clear-cut than the NUT suggested.

Jonathan Simons, head of education at the Policy Exchange thinktank, said: “It’s the same with all case law: one lawyer will say one thing and another will say something else. The only way to test it would be to take it to court.”

Asked whether the NUT would consider seeking a judicial review if the government continued on its current course, Mr Courtney said the union would “keep all options open”.

He said the Green Paper had either “misinterpreted or is wilfully misrepresenting” the legal situation, sending out a “dangerous message to academy trusts”.

If the government wants to increase the number of grammar schools, it will have to attempt this via legislation and not “by the back door”, he added.

Changing the law could be difficult. The government has only a slender majority in the House of Commons, and some Conservative MPs are opposed to grammar school expansion. The Tories lack a majority in the House of Lords.

Meopham School’s decision not to proceed with its proposal to convert to a grammar could signal a significant setback for the government’s plans, because it was taken on the basis of a consultation with parents.

The non-selective secondary near Gravesend, run by the Swale Academies Trust, issued a consultation in September asking whether it should offer “mixed grammar provision”.

The trust’s principal, Jon Whitcombe told TES that the consultation response “was as close to 50/50 as you could get”, so the trust had opted for this “halfway house” between its current arrangement and full selection.

In a letter to parents, Mr Whitcombe said that Meopham would now put in place a “grammar stream” for current Year 7 pupils from January 2017, and for new Year 7 pupils from September 2017.

A Department for Education spokesperson said: “Streaming pupils by ability is, and has always been, allowed at all schools.

“Multi-academy trusts have always been able to pool their resources to deliver these benefits on a larger scale and across different sites within the trust, and we want to see more do this.”