JERUSALEM — An estimated 1.7 million Israeli schoolchildren headed for shelters yesterday morning in response to a nationwide emergency siren as part of disaster drills that authorities said were an attempt to learn the lessons of Israel’s 2006 war with Hezbollah.

At 10 a.m., a rising and falling siren sounded throughout the country, signaling the start of the most public aspect of the week-long drills. News footage showed children filing out of classrooms under the direction of their teachers, and “injured” students being treated by paramedics and carried off on stretchers.

On Monday, Prime Minister Olmert and members of his security cabinet ran through a scenario of Israel coming under multiple missile attacks. Today, police and rescue workers in the coastal city of Haifa will practice responding to a simulated chemical plant explosion prompted by a missile attack. Officials will unveil and test a $500,000 underground shelter and disaster response headquarters built underneath the city’s central bus station. Sderot, where rocket sirens remain a fact of daily life, was the one town exempted from yesterday’s drills.