Most people, when they make a decision, believe they will get good results. But they usually also look at what will happen if they are wrong -- at the down side of their decision. And sometimes the possible consequences of being wrong are so destructive that they change their minds about what path to take. 

The chance that anybody will get polio is relatively small so it might seem reasonable not to bother having polio shots. But when people think about the possibility, however remote, of getting a crippling disease, the majority consider it worthwhile to eliminate even that small chance by having the shots.

Something similar was operating when we used to debate about developing weapons systems. Opponents said that these systems would cost many billions of dollars, and there was a very good chance that they would never be used. Supporters countered that, if we were wrong about how much protection we needed, we could be totally destroyed, and they argued that the weapons systems were worth the enormous cost.

The name of the habit of mind that leads people to consider the possible down sides of a decision is "prudence." Conservatives pride themselves on possessing it, but now, many people who consider themselves conservatives are applauding George Bush for advocating vouchers, which would permit public money to be spent on sending students to private and parochial schools. Mr. Bush says that his voucher plan would allow many poor children to go to private schools. He also claims that if public schools had to compete with private schools for students, we would see big improvements in public education. This sounds good, but it ignores the possible down sides. Here are a few things all those who are attracted to vouchers should be considering:

1. Many people think that returning to our current system will be easy if vouchers don't work out. That's not the case. Of course, only a handful of students might leave the public schools at first, but over time, classrooms will begin to empty out, and some schools and school districts will close down. Eventually, unused school buildings will be sold and converted into apartments or offices or they'll be demolished. So if vouchers turn out to be a fiasco, there will be no places in public schools for kids to go back to. And we can be sure that taxpayers won't be interested in spending billions of dollars to buy back the old schools or build new ones.

Some experiments or trials have consequences that are permanent and others do not. If you try a new kind of food and you don't like it, you don't have to eat it again. But experimenting with vouchers may be like dropping an egg to find out what will happen. There may be permanent and irreversible consequences, and we will not have a chance to put Humpty-Dumpty together again.

2. The supporters of vouchers claim there will be a great variety of new schools. Some will undoubtedly be desirable, but the ones based on race, religion or ethnicity will move us away from our common school ideal. And there will undoubtedly be lunatic fringe schools -- Jonestown of Klan or Farrakhan schools or schools where children might learn that they have a religious obligation to Murder Salman Rushdie. Some people say that it will be up to the government to deal with that problem, but courts might well uphold the schools' right to teach what they choose on the basis of religious freedom. Such fringe schools would be rare because most parents don't want their kids to learn those kinds of things. But even a few schools that encouraged violence or taught children intolerance could be very disruptive to our society.

3. Many conservatives objected strongly to school busing in the 1970s. In some cases this was racially motivated, but a large number protested because they believed in the value of neighborhood schools, and busing threatened those schools. Vouchers are a busing program for the 1990s and they still threaten neighborhood schools. Vouchers mean that the kids who live next door to you -- the ones you thought your children would be going to school with -- might choose a school across town. And to fill the seats in your local school, kids might be bused in from another neighborhood. Neighborhood schools can link families as well as children, and they can be a kind of glue that holds a community together. At a time when many people are eager to try to strengthen their communities, vouchers can lead to their being further weakened. 

People who favor vouchers claim that they will improve education. But if we try vouchers and these people are wrong, the results could be disastrous. The public schools have worked well for us for over 200 years. They've taught children from many different backgrounds to live together, and this is as important today as it has ever been. So why should we take a chance on separating kids out by race, religion and ethnicity the way private schools mostly do? Why should we further compromise our sense of community instead of trying to build it up? And why should we risk destroying the public schools when the energy and resources it would take to build and run a voucher system could be used to make our public schools what they ought to be?

Correction: The reference on August 9, 1992, to Audrey Williams College was in error. The New American Schools Development Corporation winner in question was Audrey Cohen College.