Skills gained while doing part-time jobs could count towards the diploma being planned to replace GCSEs and A-levels.
Workplace and classroom skills can often be similar
Mike Tomlinson, chairman of the government's working group on 14 to 19 education reform, said it was wrong to "ignore" real-life experience gained from Saturday or evening work.
But the question that remained was how to "give any credit" to such extra-curricular activity.
Mr Tomlinson has already suggested a unified diploma for the 14 to 19 age group in England, possibly overhauling the separate GCSE and A-level systems.
In his first proposals for a diploma, published in July, he called for more vocational study.
Mr Tomlinson told the Association of Colleges annual conference in Birmingham: "So many are in part-time paid employment, yet in terms of credit for the skills they are developing, we give them relatively little credit for that."
He stressed he was not saying pupils should be marked on whether they did their Saturday job well or not.
"If - and I stress if - we decide that one element of the diploma would be what one might call wider activities, the fact is that one thing a high
proportion of young people do is part-time paid employment.
"Some of them are in that respect part of a company's scheme of appraisal, part of the workforce and they are considered as such."
He added: "Realistically, it is for many students a real experience of work.
"We talk about wanting them to have something work-related. They are doing it, and we are ignoring it."
The diploma, if adopted by the government. would be available at four
levels from entry - equivalent to the existing entry level certificate below GCSEs - up to advanced, which would parallel existing A-Levels.
To get an advanced diploma, students may have to undertake an extended piece of research or write a dissertation.
Mr Tomlinson said about two thirds of responses to the consultation on the draft proposals were in favour of the diploma.
Many of those who came out against it were worried it was going to contain a large proportion of compulsory elements.
Mr Tomlinson insisted he did not want the diploma "prescriptive".
The idea was to ensure students got credit for studies that were both broad and deep, academic and vocational, and for extra-curricular activities such as sport, music and voluntary work.
Mr Tomlinson will publish a fuller version of his proposals in January and the final set next July.