Forty years ago this month, amid national economic difficulty and major structural upheaval in the education system, the school leaving age was raised to 16. It had taken 28 years from legislation to implementation.

Multiple postponements occurred after 1944, arising out of the struggle to cope financially and practically with the post-war baby boom. Treasury concerns in 1970 would surely have led to another delay had the education secretary of the time (soon to become legendary for her strength of will) not acted to commit the government to implementation.

None of the direst predictions of what might happen came to pass. The ROSLA (raising of school leaving age) huts did their jobs and for longer than anyone planned; truancy did not rise alarmingly; the crime rate was not affected. There were, though, complaints about the attendance, behaviour and educational focus of newly retained 15-year-olds. There were also problems with accommodation, teacher supply and - most significantly - curriculum planning.

But if something is really worth doing, it is worth doing badly. And here surely is a case in point. Before 1972, the majority took no examinations at all: 91 per cent of 15-year-old school leavers passed no O level or CSE. There was no expectation that every child should have opportunities to attain higher order knowledge, or progress to post-16 or higher education.

While it took many years before virtually every child pursued a curriculum leading to worthwhile qualifications and further learning, it is hard to imagine that point ever being reached without a universal expectation of education to the age of 16.

You do not need me to labour the parallels of economic stringency and structural change in schooling between now and then. Nor do you need me to remind you that in 12 months’ time we will see the first change to the leaving age since 1972.

There are, of course, major differences this time: college will count just as well as school; so too an apprenticeship or job with training. But we can surely learn lessons about implementation, and most importantly about curriculum and qualifications.

In important ways, 1972 made possible key changes of the late 1980s and early 1990s: the introduction of GCSEs; a national curriculum aiming to provide a broad grounding for further learning; and ultimately an accountability system based on exam performance. This time, the opportunity to rethink is obvious. The current qualifications system evolved for a world where school ends at 16 and a minority stay on. We can reset expectations now. Across the world, the most successful education systems expect the vast majority of young people to achieve at advanced level by the age of 18, whether in academic subjects or vocationally.

If we take that ambition seriously here, our qualifications system will change. With more than 90 per cent of young people staying on beyond 16, our approach to assessment at that age already looks anachronistic. And if, by 18, young people should be prepared for higher education or skilled work, the curriculum should take them in that direction and the qualifications system should reflect it. Because 16 is no longer an end point, it should not be treated as one: the entitlement to common curriculum should remain and be strengthened, but there is less need for employer-recognised qualifications at 16.

Never waste a good crisis

There are other consequences, too. Government needs to direct apprenticeship funding back towards young people, where economic and social returns are greatest, and funding should incentivise employers to train young people to an advanced level. Apprenticeship frameworks should be strengthened to require proper off-the-job training. It is indefensible that currently significant public funding subsidises employers to provide low-level, job-specific training that they already have to provide for adults they employ.

Such reforms can contribute to a much-needed national vocational route. We need a broad curriculum that keeps options open to 16. However, if we stop thinking of 16 as a terminal point, we could better begin to prepare pupils in key stage 4 for advanced study on a national vocational route, rather than focusing on completing portfolios of work for qualifications of lower value. Much of the right curriculum thinking has already been done and exists in the Principal Learning qualifications developed for diplomas.

We should likewise accept that A levels have changed and reassert the ambition lying behind the Curriculum 2000 reforms: that most should study (at least) four subjects in both sixth-form years. At a stroke that will increase challenge and differentiation for the most able while broadening the post-16 curriculum.

“Never waste a good crisis” is a superb maxim for leadership. This year’s problems in GCSE English provide an opportunity. As well as raising questions about awarding processes and standard-setting in modular qualifications, we should re-evaluate a system in which a decision to move a grade boundary (whether justified or not) can have such critical implications.

In 1971, the aforementioned education secretary, Margaret Thatcher, said to her party conference: “People wouldn’t be against the raising of the leaving age if they could be assured that... young people would learn things which would be of great use to them in... the world outside. The argument is ... about whether the curriculum in the secondary schools is satisfactory.” It took a further 15 years to introduce the first qualification intended for the whole cohort of young people. This time we can do better in seizing the moment for reform.

Jon Coles is group chief executive of the United Learning Trust and the United Church Schools Trust. He was previously director general for education standards in the Department for Education