Both the Educational Institute of Scotland and the Scottish Secondary Teachers' Association are warning that the "one size fits all" approach to public sector pensions will penalise teachers because of the physical and mental demands of the job.
The Scottish Executive is reviewing the Scottish Teachers' Superannuation Scheme (STSS), prompted by the UK Government's plans in its Green Paper, Simplicity, Security and Choice - Working and Saving for Retirement, to raise the retirement age of all public sector employees to 65. The consultation ends in January.
While teachers currently aged 51 or above will not be affected, teachers below that age who entered the profession before September 2006 in the expectation that they could retire on full pension at the age of 60 will now have to wait a further five years.
According to the EIS, more than 53 per cent of teachers retiring in 2003-04 left before the age of 60, while only 17 per cent clocked up 40 years of service.
David Eaglesham, general secretary of the SSTA, fears that in the long run teacher contributions will actually rise, despite the forecasts of government actuaries.
Mr Eaglesham said: "We will have a bigger, older generation which will be less healthy and the job won't make that any easier because it is a high-stress job. If teachers have to work until 65, their life expectancy will be reduced.
"The pupils will face the problem of having no teachers at all if their class teacher is off sick because there are growing problems in finding supply staff. Either the Government will have to legislate to increase class sizes or hold twilight classes, but the latter will just put more pressure on the same staff. The other prospect is that we will have to import teachers from abroad to make up the numbers."
Ronnie Smith, the EIS general secretary, said: "We are prepared to discuss reasonable improvements to the teachers' pension scheme, but not at the expense of existing scheme members who have joined, and remained as members, on the basis of pension promises which they believed were sound and would be honoured by the Government."
* No provision for premature retirement before the age of 55, effective from 2010. Previously the cut-off was 50.
* Pension to be based on one-sixtieth of salary with a flexible option to take up to 25 per cent of "fund value" as tax-free cash, replacing the pension based on one-eightieth of salary with a lump sum fixed at three times the pension.
* Dependents' benefits would be payable to unmarried partners, including same-sex partners.
* Spouses' pensions would be paid for life, instead of the widow's pension ceasing on remarriage or cohabitation.
* The death gratuity of two times pensionable salary would increase to three times.