There are many changes facing pupils for the new school term
Children starting secondary schools in England this week will be the first to be legally required to stay in education until they are 17.
The rise in the age at which pupils can end their studies is just one of several changes taking effect in English schools this term.
New diplomas for subjects such as engineering and construction are also being phased in.
Head teachers say too many initiatives are being introduced at once.
The increase in the education leaving age is the first such change since 1972, when it was raised from 15 to 16.
1870: First compulsory school for younger children
1880: Attendance enforced for 5-10 year olds
1899: Leaving age raised to 12
1918: Full-time education compulsory up to 14
1944: Education Act raises leaving age to 15
1964: Raising of school leaving age to 16 announced, but not in place until 1972
There are also major changes to the curriculum for 11 to 14-year-olds and to GCSEs and A-levels. The latter will have a new A* grade to help distinguish the very best exam candidates.
But the head of the Association of School and College Leaders, has warned that too much change is happening all at once.
The rise in the leaving age is part of a previously announced government policy to have pupils continue in some form of education or training education to the age of 18. This will take effect for school leavers from 2015.
As an interim step the age will rise to 17 from 2013 - the year in which those pupils starting secondary level education this week would otherwise have expected to be able to leave school.
The change will not mean that pupils have to stay in the classroom, but they will have to continue to receive training.
The changes have been introduced because ministers estimate there are some 189,500 young people aged between 16 and 18 who are not in education, employment or training.
Former headteacher Peter Inson on the changes being made
The government says this is unacceptable if the UK is to successfully compete in global business markets - but the UK's other three education systems are not adopting the new policy.
The first five new diplomas being introduced - also in England only - relate to the employment sectors of creative and media, information technology, health and social care, construction and the built environment and engineering.
Sir Mike Tomlinson, former chief inspector of schools in England, led the inquiry which recommended over-arching diplomas at different levels of attainment.
He told BBC News children would now leave school better equipped.
"Instead of just GCSE mathematics and English, we defined the idea of functional mathematics and functional English, which we said should be those mathematical and language skills that employers needed and, importantly, young people need in everyday life," he said.
Shadow education secretary Michael Gove said the idea of vocational diplomas was admirable, but raised concerns about take-up.
"Originally, we were going to have 50,000 people doing the Diploma but actually the number of students who've enlisted to do it starting this year is around 20,000.
"That's because insufficient attention has been paid to getting this examination right - politics has got in front of getting the detail right."
But Schools Secretary Ed Balls said it was right to build up the Diplomas gradually - and he was not saying they should replace GCSEs and A-levels.
"I don't think I as government should say now, I know, I'm going to make a decision.
"What we're going to do is build this up carefully in the next few years, and then we're going to let the people on the ground - the parents and the teachers themselves - make that choice," he said.
"The interesting thing, talking to IT employers for example, is they say - the computer companies - the IT Diploma, for the first time, will teach students the theory, but also how to apply computers in practical ways in business or in the public sector. And we've never ever had that in a qualification before."
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