Government-imposed floor targets should be replaced by “more ambitious” goals set by schools themselves, according to the country’s biggest heads’ union.

Delegates at the NAHT annual conference in Birmingham backed a radical manifesto for the future of education, which included replacing minimum standards of exam performance with “paths of improvement” tailored for individual institutions.

In last year’s performance tables, 767 primary schools - 6 per cent of the total number - failed to meet the floor standard of 60 per cent of pupils attaining at least Level 4 in reading, writing and maths.

At GCSE level, 154 secondary schools failed to meet the minimum standard of 40 per cent of pupils achieving at least five GCSEs at grade C or better, including English and maths.

In his speech this afternoon, general secretary Russell Hobby told delegates: “The trouble with floor standards is that they cannot be set high enough to be inspiring.

“If you set them at a reasonable level, they look unambitious. If you make them ambitious, you trigger widespread and unnecessary disruption.

“Floor standards have reached the end of their utility. We suggest a different approach, which we have called the ‘path of improvement’. This has two ingredients: a genuinely ambitious target and a sustainable rate of improvement.

“Every school has its own path to the target based on a reasonable, evidence-informed rate of improvement. While the school is on the path, it is free from threat of intervention and each school progresses over a different timescale to the same goal.”

Delegates also backed a motion calling for reformed GCSEs, A-levels and vocational qualifications to include an “appropriate balance between knowledge, understanding and skill acquisition”.

Alan Mottershead, head of Trinity School in Carlisle, said the move from regular assessment to high stakes, end-of-course exams between Key Stage 2 and Key Stage 4 risked creating a “five-year programme of examinations”.

“The damage that this may do to a broad and balanced curriculum across the secondary phase, in particular in GCSE and A-level years, is incalculable,” he said.

Mr Mottershead also argued that exams could become more focused on “memory recall” than understanding, adding: “Exams will be even more of an unreliable and unrepresentative picture of a student’s work or real ability.

“It will also deny the richness, exploration, curiosity, wonder, questioning and many other things which characterise a real education. They will be replaced by, ‘learn this and make your answer book like that’.”

Despite the strong backing for scrapping floor targets, conference delegates watered down some of the union’s other proposals, including reducing the length of the summer holiday and spreading breaks more evenly throughout the year.

While 55 per cent of members backed plans to explore altering term structures, members decided in a private session that further research should be carried out first.

Members also amended controversial proposals to give admissions priority to children eligible for free school meals, deciding that an impact assessment should be carried out before a final decision is made.