A "one size fits all" education system is failing some of England's children and more must be done to ensure they get the schooling they need, according to Sir Michael Wilshaw.
It is important not to forget that the "written off and the 'failed'" need the most help, and the responsibility to support them does not end when students fail to achieve the academic targets set out for them, the Ofsted chief suggests.
In a speech to the CentreForum think-tank on Monday, Sir Michael will argue that less academic youngsters deserve a good education, and that not enough is being done to pursue a more technical path.
He suggests that other nations, such as Germany and Switzerland, have more flexible education systems that meet the needs of both students and their economies, and as a result they have lower youth unemployment levels than the UK.
In his address, Sir Michael questions what should be done about the quarter to a third of youngsters who do not meet challenging academic targets.
"Even when I was head at Mossbourne Academy in Hackney, which had a great academic reputation, 20% of youngsters failed to reach our targets," he says. "Most of them went to a local further education college, usually a large, impersonal and amorphous institution, and did badly.
"As somebody who was motivated by moral purpose, I always felt that I was letting down a significant number of good children who deserved better. Talk to any good secondary head and they would say much the same.
"Yes, our ambitions should be bold. But they should be inclusive too. Our responsibilities as educators do not end when students fail to attain our targets. On the contrary, the written off and the 'failed' need our help most and we should never forget it."
Sir Michael will also say: "The great comprehensive school headteacher knows that a 'one size fits all' model of secondary education will never deliver the range of success that their youngsters need.
"Some of our international competitors understand this probably better than we do.
"Their education systems are more flexible than ours and are much more geared to aligning the potential of the student with the needs of their economies. As a result, countries with excellent academic and technical routes have far lower youth unemployment than we do.
"Despite six years of economic recovery and falling unemployment, youth unemployment in the UK still stands at 12%. In Germany it is 7% and in Switzerland 3.7%."
He goes on to say that there is a need for a strong, core academic curriculum, and that there should be no trade-off between academic study and specialist vocational training.
"There is no good reason why the vast majority of pupils shouldn't have mastered basic maths and English at primary and a Grade 5 at GCSE," the Ofsted chief says.
"However, we should never forget the minority who will never do so, nor the larger number who may pass but who do not wish to pursue a wholly academic path. They too deserve an education worthy of the name. The country cannot continue to fail half its future."
He also warns that too many students are being left behind at age 16 and left disadvantaged because of "uniformly weak" careers guidance and poor preparation for the world of work.
And he suggests: "Our system is adept at guiding students into higher education. But it still struggles, despite the recent focus on apprenticeships, to inform them about alternatives to university. We simply have to improve the quality of our technical provision and present it as a valid educational path if we are to equip youngsters with the skills they need and employers want."
Sir Michael's speech comes amid a continued push by the Government to encourage children to study traditional subjects, including English, maths, science, a foreign language and either history or geography, up to GCSE. Ministers have argued that studying these subjects will give children a good grounding for their future.