Students with term-time jobs are more likely to fail their degree than those who are not employed, according to a large survey of students.
Researchers from Northumbria University discovered that students with jobs get "significantly" lower examination grades and may be twice as likely to fail, although the authors stress they have not proved any direct causal link.
The study compared the performance of almost 900 students, half of whom had worked at some point during the academic year.
More than a third of the employed students admitted missing timetabled academic sessions as a result of their work commitments, though the real figure could be higher.
The research found that socio-economic status was a key factor. Students from less affluent backgrounds - as indicated by grant and fee status and self-reported social class - were more likely to take on term-time work and to work longer hours than students from better-off families.
Just over half the students in employment received a financial contribution from their parents compared with 80 per cent of non-working students.
The most commonly cited reason for working was to achieve a better standard of living. But many students said working was an alternative to borrowing money and almost half the sample said they needed their jobs to remain at university.
A smaller proportion said they were working to achieve a degree of financial independence from their parents. Only 9 per cent of the sample said their job was related to their future career objectives.
The research also uncovered differences in working patterns according to where students lived. For example, students living at home were twice as likely to engage in paid term-time work compared with other students. The researchers said this was likely to be because such students tended to be less affluent, although some could be continuing jobs they had had before college.