UP to 60,000 of the country's estimated 100,000 schools are crumbling and could collapse at any time.
According to deputy education minister Mohammed Afshari, the future of "old and non-standard schools" is in jeopardy as a result of cuts in the building budget.
A senior education ministry official said that of 390,000 classrooms in the country, 47,000 were "unusable". At an estimated 2,000 schools, classes are held outside or in classrooms without ceilings that cannot be used in bad weather.
Western diplomats in Tehran say, Iran has focused on tackling rising unemployment by investing in job creation at the expense of education.One said state schools were "overcrowded, understaffed and lacking appropriate facilities".
More than half of the worst buildings are in rural areas, where standards are much lower. Child literacy in towns is 20 per cent higher than in more remote areas.
Iranian children are legally obliged to attend school - which is provided free for the first five years. But many youngsters from poorer families still work instead.
Attendance drops at intermediate and secondary level when parents have to make a financial contribution. Families invest more in sons' education than daughters'.
Officials say at least 27,000 new classes need to be set up every year to meet growing demand from a fast-expanding population. But a lack of funds means that it is not possible to establish more than 15,000 classes.