Teacher training leaders have expressed concern after it was revealed that trainee teachers are working for more than 21 hours a week on top of their courses.
Trainees say they are taking on extra paid work in an effort to stem spiralling student debts of more than pound;20,000.
Many say the extra cash is vital to pay for the basics, such as food, with nearly half saying they have gone without equipment or books due to lack of money.
A study showed that nearly a third of trainees have had a paid job, with one in 10 of those moonlighting for 21 hours or more to pay their way through training.
Nearly a third of those with an extra job said they worked between 11 and 20 hours on top of their full-time courses.
The trend is thought to be adversely affecting some students' college work, with the vast majority saying it affected their energy levels, and many saying it hit their social lives and family relationships.
Professor Roger Woods, dean of education at Birmingham City University, who is also chair of the Universities' Council for the Education of Teachers, said among undergraduates there was a "culture and expectation" to work alongside study.
But PGCE students, he said, would find it very difficult to fit in extra hours without negative consequences.
Professor Woods said: "I would be very concerned about any student putting in more than 20 hours. We discourage postgraduates from working, but we do not impose a blanket ban if students can fulfil their study requirements."
He said working with children or tutoring could reinforce study, but students could fall down if they were working two or three nights a week alongside teaching practice.
"We have had students get into a mess when they have tried to do this because teaching practice is a full-time job," he said.
He added that the survey, carried out by teaching union the Association of Teachers and Lecturers (ATL), highlighted the need for bursaries to be protected from cuts.
The Training and Development Agency for Schools recently announced that bursaries for most subjects will be cut from September, with allowances for priority subjects such as science and languages slashed from pound;9,000 to pound;6,000.
Students studying non-priority subjects such as PE will see their current bursaries of pound;6,000 cut to pound;4,000.
Nearly a third of the 500 student and NQT respondents said they would owe more than pound;20,000 by the time they start out in work.
Lewis Newton, a student from Rotherham, said: "I am concerned about the debt that I will leave university with.
"Students should not have to start out in life with huge debts of up to pound;30,000, just for training to become a teacher in order to better themselves and to have a worthwhile career."
Another student teacher from Cumbria said: "Basically, it's not a choice when it comes to having a part-time job. I wouldn't be able to pay my rent or buy food or all of the books I need for university if I didn't have a job."
Other teachers complained that it was unfair that trainees had to pay tuition fees when those training in other public services, such as the police, did not.
However, only 18 per cent of student teachers and NQTs said they had financial regrets about taking up teacher training.
Rebecca Stokes, a student from Cheshire, said: "Although I have financial issues, I wouldn't let that get in the way of my feelings regarding my desire to become a teacher."
Mary Bousted, general secretary of ATL, said: "I think everyone understands that you will be in debt after any higher education course, but if students have to do long hours of paid work to support their studies, their grades will undoubtedly suffer. This is not in anyone's interests."
She added that she was "fiercely against" further increases in tuition fees in case a career in teaching became "an impossible dream" for children from poorer backgrounds.
Everything will be ok after PGCEVERYTHING WILL BE OK AFTER PGCE: `BUT IT'S NOT'
Ashley Dickey, 25, is in her second year of teaching, but is still saddled with debts of around pound;25,000.
Unable to get a permanent job where she lives in Northern Ireland, she works as a special needs supply teacher two days a week, supplementing her income with three of four evening shifts a week as a hotel waitress.
Her income is so low that she is still only paying off the interest on her student loan.
Although she can pay for the basics in life, financial worries still hang over her, and there is no spare cash for luxuries such as trips away, she said.
"I'm not struggling, but I have to be extremely careful with my money because I don't know what I will be paid the next month," she said.
Ms Dickey, who is also chair of the Association of Teachers and Lecturers' forum for student and newly qualified teachers, said the Government should make more use of "golden handshakes" and bursaries, and that trainees should be given financial incentives for completing their PGCE courses.
She said: "You always sit there saying, `I'll get myself through the PGCE and then everything will be OK.' But it's not.
"I really enjoy teaching, but you always have the money worries hanging over your head. You start thinking about what other jobs you could be doing for more money."
She said the situation of many colleagues, especially those who cannot find permanent jobs, is much worse.
"Some of them are just doing everything they can to keep themselves afloat," she added.
Original paper headline: Studying by day, pulling pints by night: trainees stem pound;20k debt