It's hard to redesign an airplane while you're flying it -- and almost impossible if you're trying to dodge anti-aircraft missiles at the same time. But that's what we're expecting teachers and other school people to do right now: reform their schools while they tough it out through threatened and actual layoffs and budget cuts. Here's what's happening in a number of places across the country:

• Last winter, teachers in Boston, who had committed themselves to school restructuring, were suddenly faced with the possibility that the city would renege on their new contract. That crisis passed, but now, thanks to a city ceiling on school funding for 1991, 800 teachers have received layoff warnings. Because the school district is still under court-ordered racial hiring quotas, teachers with 20 years' experience could lose their jobs to teachers with one or two years' experience. So besides having staff cuts to deal with, Boston teachers will probably have to cope with renewed racial tensions.

• Statewide in Massachusetts, 9,000 teachers -- one fifth of the public school teaching staff -- have gotten layoff notices for next year. Last summer, 5,000 Massachusetts teachers got these notices.

• In April, it looked as though schools in Texas would have to close because of a battle over a school finance reform bill. The legislature tried to solve the problem by passing a second bill, but Governor Clements vetoed it this week so the uncertainty remains.

• Schools in New York City face underfunding by the state and cuts in city funds that endanger the ambitious school reform that is just getting started there.

• In North Carolina, school districts have to find unspent money from this year's budget to the tune of nearly $40 million to help cover a shortfall in state funds. Some say the only way they can do it is by closing their schools or by cutting their summer school programs.

The reasons for these budgetary crisis vary, but whatever the reasons, schools in many parts of the country are going to lose funds and lose staff And the situation is especially troubling because of the impact it could have on school reform.

Things have been looking hopeful. We have a set of national education goals that acknowledges several of our big problems. We have a number of promising school reform efforts under way -- some on the local level and some, like the new Kentucky reforms, on the state level. People seem to be rejecting the kind of top-down reform that was popular a few years ago. Schools are beginning to get greater control over what they teach and how they teach it. But everything is still experimental. We really don't know yet what's going to work to make our schools more productive. However, we do know one thing. Change is extraordinarily difficult, and we're not going to achieve it if schools move from one crisis in funding to another.

To make the kind of change we need, teachers have to think and read and talk together to find new ways of reaching kids who now see school as a dead loss. Teachers, administrators and community people have to devise new ways of governing schools. They need structures that enable them to work as allies instead of adversaries. And everybody needs to think about new ways of delivering education.

Is the seven or eight-period day the best way of structuring time for learning? Maybe several long periods would work better. And maybe the current course structure needs rethinking. Instead of putting students together in classes to study a subject for a semester or a year, what about guided, independent study similar to the way Boy Scouts earn merit badges? What about using technology to individualize learning? And what about reorganizing the teaching staff to make use of a lead teacher, paraprofessionals and volunteers as well as regular classroom teachers?

There is no shortage of good ideas for restructuring our schools so that all our children can learn better. But finding which ones work and which are duds will require time; it will require the creativity and devotion of everyone who works in the schools -- especially the teachers. And you're not going to engage these people in bringing about change if they don't know whether their achievements will survive the next budget crisis -- or whether they'll even have a job next year.

Unfortunately, the assumption that we can slash school funding and expect the people who are left to carry on ambitious school reforms is nothing new. I recently came across a column I wrote in April 1971, nearly 20 years ago, during a financial crisis in New York City. The situation I described then could be the one I'm describing now:

" ... the crises we have faced and are now facing make a mockery of the current talk of accountability and the restructuring of education .... How can we reform education while preoccupied with fighting off disastrous budget cuts?

"If we are to have educational reform and a responsible program of accountability, we need more than a solution to this immediate crisis. We need a long-term commitment of funds from federal, state and city government so that educators, parents and community groups can devote themselves to school improvement instead of the unrelenting battle to hold onto what they already have."