The Education Ministry issued new instructions yesterday obligating school principals to report daily on student and teacher absences as part of the effort to address concerns about swine flu.

Yesterday only 20 of the 185 students reported for class at Tel Aviv's Ussishkin Elementary School. On Sunday, the parents' committee urged parents to keep their children home, after more than 120 students came down with influenza.

On Tuesday a senior Health Ministry official said the ill students were presumed to have swine flu, as seasonal flu season has yet to begin in Israel.

In the letter to principals yesterday, Education Ministry director general Shimshon Shoshani wrote that "the incidence of swine flu in Israel is similar to that around the world, and it is increasing in the United States and Europe. The disease has not become more serious, but many light cases are expected."

Three Ussishkin students and an administrator have been diagnosed with swine flu thus far. The head of the school's parents' committee, Ramit Frankel, said the school building would undergo a thorough disinfection today and tomorrow.

"The disease is still being examined," Frankel said. "It's irresponsible to send children to school given the situation."