Graduates who become teachers and stay in the classroom for their whole career will never pay off their student loans, a union has claimed.

The Association of Teachers and Lecturers (ATL) told TES that, as a result of the introduction of £9,000 university tuition fees in 2012, teachers who progress to the top of the upper pay scale “will be saddled with a lifetime of debt, will never pay it off and leave the taxpayer to pick up the tab”.

The union’s calculations are based on the assumption that an average teacher starting out in the profession in 2015 would have an initial debt of almost £50,000, made up of three years of tuition fees plus maintenance loans and compound interest.

A set proportion of graduates’ income is then deducted from their pay until the loan is paid off. However, the unpaid balance of the debt is automatically written off after 30 years.

At this point, ATL has calculated that the average teacher at the top of the upper pay scale would have forked out more than £52,000 in repayments. However, it reckons that the government would still be left with a massive shortfall of £111,000 for every teacher, due to the interest accumulated during the previous three decades. 

Martin Freedman, ATL’s director of economic strategy and negotiations, said the “incredible” figures could deter young people from entering the profession.

“It’s another off-putting factor for people who are thinking of going into teaching,” he said. “We’ve got pay freezes, increases in pensions contributions and now higher student loan repayments. If you really want to buy your own house, you’re not going to go into teaching.

“We need more people to go into teaching, as there is a higher number of kids coming through, but we seem to be doing everything possible to put [prospective teachers] off.

“It seems a pointless exercise. Teachers will have to pay back more money, yet the government will end up picking up the tab. It’s incredible, really. It would be cheaper for the government to pay the tuition fees up front.”

Even teachers on the bottom rung of the main pay scale (around £21,804) would be above the student loan threshold, meaning they would be making repayments from their first pay packet.

The annual sum of the repayments would increase from £72 (during the first year of teaching) to £2,577 in the 30th year at the chalk face (for a teacher earning £65,927 at the top of the upper pay scale).

In total, then, a teacher who gradually rises from the bottom of the main pay scale to the top of the upper pay scale during their career would, according to ATL’s projections, pay off  £52,141 of their loan, leaving the government to take a £111,559 hit.

And with more than 25,000 new teachers currently entering the profession each year, the government could well end up with a multi-billion-pound headache come 2045.

The assumptions on which ATL’s calculations are based - that the teacher’s salary would increase by 2 per cent each year, with interest on the outstanding loan balance simultaneously going up by 5 per cent annually (on the basis of the RPI measure of inflation being 2 per cent) - are by no means set in stone.

But Mr Freedman told TES that the consequences of the rise in tuition fees were nonetheless clear. “The teacher who does not become a school leader will be saddled with a lifetime of debt, will never pay it off and leave the taxpayer to pick up the tab.

“If the teacher goes abroad (where the Student Loans Company will not be able to chase them) or takes time out to raise a family (70 per cent of teaching workforce are female) the situation will be much worse.”

A spokesman for the Department for Business, Innovation and Skills said that graduates would not have to start repaying their loans “until they are in well-paid employment”.

“The loan scheme has many features of a graduate tax,” he added. “Better paid graduates pay back more, while others have some of their loan written off. Independent research shows the new loans are more progressive and monthly repayments will be lower than before. Going to university remains affordable for students and it is based on their ability, not their ability to pay.”