Shortages in the two key subjects of English and mathematics are driving the U-turn and it may be in place within a year. Universities report this week that they are struggling to expand teacher training places next session in their priority subjects.
This is bad news for ministers who are committed to class size cuts in English and maths in S1 and S2 and who need an estimated extra 450 teachers in each subject simply to meet their pledge.
Tighter entry standards, for example, have ruled out many students with engineering degrees who previously ended up teaching maths in schools rather than building bridges.
The Scottish Executive is acutely aware of the impending staffing crisis and is reviewing the stipulation introduced in 2000 that students should have three years study in their main subject at university before moving on to teacher training.
Engineers have been caught by this. Previously they could study maths for two years and still qualify but the General Teaching Council for Scotland, with government backing, raised the barrier in defence of higher standards.
Some universities were opposed but were overruled.
Teacher recruitment realities and the rapid development of new undergraduate courses is now forcing ministers to rethink entry requirements.
A spokesman for the Executive said that the current review of teacher training would pick up many of the issues, such as changes in the content of degrees and whether they were still relevant to teaching.
He said: "We are also committed to recruiting an additional 3,000 teachers by 2007, in part to help reduce English and maths classes in S1 and S2 to 20, and need to ensure we are not allowing potentially high-quality teachers to slip through the net."
Matthew MacIver, the GTC's registrar, admitted the council was in talks with the Executive but placed a different slant on the changes to entry requirements.
"What we are talking about at the moment is how the huge expansion of degrees in the higher education sector might change the way that we set out what is needed to get into the profession. That is simply a sensible way of looking at the whole new world of higher education," Mr MacIver said.
"New degrees and new subjects in the curriculum require us to review entry requirements regularly. These discussions are not about shortage subjects, they are about how to attract the best candidates into the profession."
While they are mulling over entry requirements, ministers will be heartened by early applications for postgraduate teacher training courses that begin in August. Applications for primary and secondary courses are up by more than 9 per cent, countering the view that teaching is not an attractive profession. The problem is finding enough students to fill the priority subjects.
Joe Kilgariff, registry head at Strathclyde University, said it currently had 52 applicants for English but only 34 for maths. Some had already been rejected. Last year there were 50 places for English and 40 maths but universities are under orders to expand. Mr Kilgariff said they would recruit up until the summer.
Other subjects such as history, modern studies and music are full and some students have been turned away. High-quality candidates for the primary course have also been rejected.
Strathclyde is the largest trainer in Scotland and confirms a 9 per cent rise in applications for the primary course over last year and 15 per cent in secondary. But the ratios of applications to places are vastly different. In primary it is 4:1 but in secondary "almost 1:1", Mr Kilgariff said.
At Aberdeen University, Cathy Macaslan, education dean, said its recruitment campaign was still running. "It's looking better but maths and English will still be a challenge," she said.
Primary postgraduate applications for the one-year course are up by 10 per cent and secondary by 3 per cent.
At Edinburgh University, applications for secondary one-year courses are up 10 per cent but the figure for primary is steady.