Opponents of Israel's planned withdrawal from the Gaza Strip have chained shut 167 schools and nurseries in and around the city of Tel Aviv.
Protesters want to sabotage Israel's withdrawal from Gaza
Police were called after security guards and teachers who arrived for classes found themselves locked out.
It is the latest in a series of actions by protesters who have vowed to sabotage the pull-out, slated for July.
The army meanwhile has placed a leading opponent of the withdrawal under house arrest until September.
Noam Federman, a member of the outlawed anti-Arab Kach movement, was ordered to remain at his Hebron home because the authorities consider him a security risk.
Israeli media say it is the first time the military has issued a ban on an individual to prevent them from protesting against the pull-out.
Police spokesman Yossi Avendi said activists had placed small locks and chains on gates and doors on schools from Bat Yam, south of Tel Aviv, to Herzliya, to the north.
Placards reading "Jews don't expel Jews" were also hung on the gates.
Federman is a leading opponent of the pull-out
Firefighters were called to break through the chains with heavy cutting equipment.
"We don't know who it is, but it is anti-pullout people because they left leaflets behind against the withdrawal," Mr Avendi said.
Israeli Education Minister Limor Livnat demanded police catch those responsible.
"This is violent unruliness that should not be ignored," Israel radio quoted her as saying.
Opponents to the withdrawal have recently stepped up protests against the plan, including blocking a main highway in Tel Aviv with burning tyres on Monday.
Under the plan, Israel will pull all 8,000 Jewish settlers, and the Israeli troops who protect them, from Gaza, while keeping control of the borders, coast and airspace.