The country’s most academically successful comprehensive is to opt out. Gillian Shephard, the Education and Employment Secretary, has told the Blue Coat School in Liverpool it can go grant-maintained at the start of next month.

Her decision on the proposal, which was submitted to the Education Secretary last July, means that a Labour front-bench education spokesman will find himself in the embarrassing position of having a son at a GM school from the middle of the school year. Peter Kilfoyle, MP for Liverpool Walton, is an outspoken opponent of grant-maintained status and was involved in a previous campaign to stop the Blue Coat School opting out. He claims to have rejected another school for his elder son when it went grant-maintained.

The 700-strong Blue Coat School regularly takes the highest position in exam league tables of any state comprehensive. Last year, 97 per cent of 15-year-olds at the school gained five or more A to C grades, a small but tolerable drop from the previous year, when 98 per cent achieved that level.

Welcoming Mrs Shephard’s decision, Peter Healey, chairman of governors, said the school would be better as part of a family of 1,100 GM schools than “out on its own”. The school was established as a charity in 1708 but has no church or large foundation behind it.

It has been repeatedly at the centre of controversy in recent years because of its selective admissions procedure, defended by the head and chairman of governors on the grounds that the school is massively oversubscribed. The Labour-controlled city council tried to close the school 11 years ago, when Derek Hatton was leader, but the council’s proposal was rejected by Sir Keith Joseph, then Education Secretary, after massive opposition from parents.

Then Gillian Shephard, the Education Secretary, took the school to task for its insufficiently “transparent” admissions procedures. She told the school either to stop choosing pupils through interview and recommendation from primary heads or to apply formally to become selective. Critics had complained that its ranking in exam league tables was unfair to other comprehensives because its procedures amounted to covert selection.

When the school opted to apply for fully selective status, Mrs Shephard took more than a year to decide to let it go ahead, amid threats from Liverpool City Council about seeking a judicial review.

The council complained that selection at the school, which takes only boys from 11 to 16 although it has a mixed sixth form, could place the authority in breach of the Sex Discrimination Act as girls would be denied a grammar school place.

Now the school finds itself in the “family” of GM schools and thus safe from a left-wing council, but just before an election likely to bring in a Labour Government. Labour has promised to alter the status of opted out schools, bringing them back into partnership with local authorities.

The future of selective schools would be decided by a ballot of the parents affected. So it may be that next week’s entrance exam, when 494 candidates will compete for 120 places on a first-past-the-post basis, will be the first and the last.

The school’s earlier attempt to opt out two years ago was defeated when more than half the parents voted against. This time, said Mr Healey, the staff were strongly in support of the move and 70 per cent of the parents voted in favour. But the application to the Secretary of State took six months to be approved because the city made various objections to the way in which the meetings during the opting-out campaign had been conducted. The school had originally hoped to go grant-maintained on New Year’s Day.