NEW YORK (AP) _ Condoms and curricula dominated the education debate here in recent years. But while arguments over morality and multiculturalism raged, a more pressing schoolhouse problem went unnoticed - asbestos.

It's getting plenty of attention now, as city officials scramble to clean up a mess that threatens two-thirds of the public schools in the nation's largest system.

They also face another daunting problem: allaying the fears of parents about their children's safety.

The revelation nine days ago that a decade's worth of asbestos testing was worthless left officials groping for words. ''Breathtaking,'' offered Deputy Mayor Norman Steisel. ''Astounding,'' said Thomas D. Thacher of the School Construction Authority.

Overwhelming was more like it. What started out as stunningly bad news quickly evolved into even worse news. The scope of the problem was far beyond what city officials initially believed, raising the possibility that some schools will not open as scheduled Sept. 9.

Mayor David Dinkins vowed that no school will open until it receives a clean bill of health. ''Operation Clean House,'' a joint effort of city agencies, is hiring subcontractors and dispatching 40 teams of inspectors to locate and clean up asbestos.

Despite their efforts, barely 25 percent of the city's schools had been visited by Friday. Only seven schools were fully inspected; asbestos was found in all seven.

The scandal, which is under investigation by federal authorities, is the latest blow to a beleaguered school system in which only 42.9 percent of the high schoolers enrolled in September 1988 graduated in four years.

A search is under way for a new chancellor. The outgoing chief, Joseph Fernandez, was ousted following a contentious debate over condom distribution in high schools and a controversial elementary school curriculum that included acceptance of gay men and lesbians.

The asbestos problem now has overshadowed those discussions. Initially, the city said 714 of its 1,069 schools showed evidence of possible asbestos problems.

Further investigation showed schools initially believed clean were not, while those which could be tainted were worse than first believed.

What went wrong?

An asbestos task force, responsible for checking city schools for the cancer-causing material, was never monitored; it completely botched the job, a city report said.

No problems were uncovered until the authority, in routine work, turned up asbestos in 70 locations that had been certified as clean between 1989 and 1992. The subsequent investigation revealed the system-wide abuses.

The workers involved - 53 Board of Education employees and their director - were reassigned to new jobs. Dinkins also canceled four dozen city contracts with Enviro-Safe, a Manhattan company hired to oversee the asbestos testing.

Even as it cleans up, the city is trying to convince adults the problem is under control.

''This is all about these kids going to school in September in a safe, healthful environment,'' said Harvey Garner, the acting schools chancellor, a day after angry parents blasted the Board of Education in a public meeting.