eaders of the nuclear freeze movement, having seen their efforts meet or exceed expectations nearly everywhere except the White House, have one question on their minds these days: What next?

Wisconsin peace activists have an answer. A grass-roots movement toward "nuclear free zones" has captured the fancy of the state, and already has -- in theory, anyway -- freed one Madison High School, a number of stores and private homes, and a congressman from the threat of nuclear war.

The next target is a "nuclear free Wisconsin," with the aim of banning nuclear wastes and anything related to nuclear weapons from the state.

It's intentionally symbolic, of course, the idea that a home, school or community can be declared nuclear free. It is a way to say, "We don't want to be a target and we don't want any part of the arms race," in the words of one local freeze organizer.

"But at the same time, if we get enough response and official action, ordinances and resolutions adopted, it may grow beyond symbolism," said Bill Christofferson, spokesman for a Madison-based peace group called Nukewatch.

A social studies class at Madison's Malcolm Shabazz High School led the way this fall by convincing 90 percent of the student body, and most of the teachers, to sign a petition declaring the school a nuclear free zone. The students carried the petition to Washington, where they were received politely at the Pentagon and the Soviet Embassy, and all but ignored at the White House.

The same class also invited Rep. Robert W. Kastenmeier (D-Wis.), to a discussion of ways to end the arms race. Kastenmeier, a strong supporter of a nuclear freeze and a critic of President Reagan's defense policies, left wearing a "nuclear free zone" button.

"I'm going to have to think about the ramifications of walking through Congress as a nuclear free zone," he said.

The Madison Board of Education is being asked to declare the entire school system nuclear free, and in Green Bay a movement is afoot to do the same for the University of Wisconsin campus there.

Ten states have voted on the nuclear freeze question, and all but one -- Arizona -- approved it by large margins. About 30 cities, towns and counties, from Miami to Cook County, Ill., and Denver also have voted for a freeze.

Wisconsin voters passed a nuclear freeze referendum in the primary election last Sept. 14 by about 80 percent. Even before the vote, it was endorsed by all three candidates for governor, both houses of the state legislature, most of the state's congressional delegation, and a number of city, county and town boards.

With such a track record, Wisconsin freeze campaign leaders were deluged by requests for advice from peace groups all over the country. In response, Nukewatch established itself as a clearinghouse for information on both the freeze and the question of where to go from here.

"Now we have to keep the momentum going, give those people who were working on the freeze campaign a way to stay involved," Christofferson said.

The idea did not originate in Wisconsin. The Shabazz High School students were inspired by two Maryland towns, Garrett Park and Sykesville, that earlier declared nuclear free zones. And the town of Ashland, Ore., passed a referendum on Nov. 2 establishing a jail term and fine for anyone violating its nuclear free status.

But here people seem determined to retain what they see as their leadership status in the anti-nuclear movement. That feeling was manifested recently when the Dane County board rejected Reagan's crisis relocation plan, on grounds that it made no sense to evacuate Madison residents in the event of nuclear attack.

Two Madison hospitals and the University of Wisconsin Medical School also rejected a Pentagon plan for civilian hospitals to treat military casualties in the event of war with the Soviet Union, saying such a war likely would become nuclear and medical treatment would be futile.

About 100 representatives of state peace groups attended a "Nuclear Free Wisconsin" conference here and Nukewatch has completed mailings to an additional 1,200 peace and anti-nuclear groups around the country.