Nearly two-thirds of students work during the academic year to make ends meet and stave off debt, according to a report.
A small proportion of students' employment forms part of a structured work-experience programme, but most of it is ad hoc, with questionable value, other than short-term financial gain, researchers have concluded.
Students from poorer backgrounds are more likely than their better-off peers to be doing ad hoc paid jobs during term time, according to the report from the Open University's Centre for Higher Education Research and Information and the University of Central England's Centre for Research into Quality.
Although data on student work experience are scarce, research commissioned by the Higher Education Funding Council for England pulled together information from a wide range of sources.
A national survey found that 60 per cent of students had worked during the academic year, with about half working an average 11 hours a week in term time. About 80 per cent were also working during the summer vacation.
The growing number of students living at home with their parents were the category most likely to do term-time work (69 per cent). Those with children were least likely (40 per cent).
The survey found that 54 per cent of the bottom two social classes worked in term time, compared with 44 per cent from the top two.
Lee Harvey, director of UCE's Centre for Research into Quality, said that even ad hoc work could be useful if students were encouraged to think about and write down what they had learnt from the experience.
"What kind of work experience is useful partly depends on the employer, but, in general, it is best to do something where you have to work as part of a team, be flexible and deal directly with customers, rather than something like sitting at a checkout all day," he said.
But the report says only small numbers of students are taking part in organised work experience external to their programme of study, which aims to help students identify what they have learnt from their work experience.
Students' reluctance to take part in organised schemes may signal that some employers do not fully recognise such programmes.
The report says that if this is the case, "it seems likely that students will continue to seek work experiences that maximise short-term financial gain. Learning may still take place, but its nature is likely to be ill-defined and not always recognised either by the graduate or by the employer."
The report notes that there is little systematic collection of data on the type of work experience students are doing. It recommends that higher education institutions be encouraged to monitor it and to find out why students are reluctant to take part in some organised forms of work experience. "This might be particularly important for those institutions that make claims about enhancing the employability of their students," it says.