The man reviewing 14-19 qualifications in England says students might have to be forced to study certain subjects to avoid over-specialising.
Mike Tomlinson also investigated last year's grading furore
Too narrow a focus at A-level remains a criticism of the present system.
The introduction of AS-levels in the first year of post-16 study was supposed to tackle this, but has not done so.
Mike Tomlinson, former chief inspector of England's schools, is considering the government's plan for an English version of the Baccalaureate, a single qualification taken at 18.
His final report will not be ready for another year, but he gave a progress report to sixth form and further education colleges in Cambridge on Wednesday.
Ahead of that, he said his review team was considering new ways to broaden the scope of study at this age, perhaps by introducing compulsory subjects.
So a student taking history and geography could be told they had to study statistics, and someone taking business studies could be made to take a modern foreign language.
Opponents of an English Bac argue that it would mean abolishing GCSEs, taken at the age of 16 - at the end of compulsory education.
But that could mean teenagers who leave school at 16 would have nothing to show for 11 years at school.
One idea floated by Mr Tomlinson is a system of credits which would enable a 16 year old to leave with an exact description of what they had achieved in the subjects they had studied.
This would enable them to pick up where they had left off if they decided to return to education later.
But such radical change would take years to implement.
The review is also expected to recommend some shorter-term changes to take pressure off the overburdened examination system.
Coursework for GCSEs could be slimmed down - perhaps allowing students to do one wide-ranging project, rather than submitting written work in the eight to 10 subjects taken by many pupils.
The government set out its ideas in January in its policy document 14-19: opportunity and excellence.
Among other things this proposed reducing the amount students had to do between the ages of 15 and 16 "to the minimum essential for future progression and personal development".
There would be a greater emphasis on work-related courses, where appropriate.
A poll by the Association of Colleges, published on Wednesday, found that a fifth of students wished they had started college at 14, rather than 16, because of the more adult environment on offer.
Meanwhile, 51% said vocational courses were more enjoyable than purely academic ones.
The AoC interviewed 226 students from England for its survey.