Desegregation will come to Cambridge, one way or another, next fall. But school superintendent William Lannon's announcement last week that he had chosen redistricting as his method surprised much of the community and angered some residents and school board members.

Only three weeks ago, school committee members asked Lannon to go instead with "Plan B"--which would have paired city schools so students would attend kindergarten through third grade at one building and fourth through eighth grade at another.

The school board members argued the pairing plan would be "educationally more sound" and would spread the effects of desegregation across more of the city's students, rather than concentrating the impact arbitrarily on a few.

Many city residents agreed--night after night parents from many of the city's elementary schools reported to the superintendent that the consensus in their neighborhoods was that Plan B was the lesser of three evils.

Lannon said last week he chose the redistricting--"Plan C"--because Plan B would make closing schools difficult if enrollment declined, and because a "re-evaluation of statistics" showed the pairing proposal might not work after all.

"We were afraid that we could do it, and that in five or six years the population would change enough that we'd have to go through the same thing all over," Lannon said.

Another factor in the decision may have been the fear that teachers would not cooperate with the pairing plan, which would create middle schools instead of the two-schools instead of the two-school current system.

Now that he's made the decision, Lannon may have the school committee in a corner. Even those members who still disagree with the decision concede that too much overt fighting will make desegregation more difficult than it already threatens to be.

At least one member, though said last week that change is still possible. Many parents as well have said they will tell the committee they don't like Plan C at another round of public hearings scheduled for late in May.

"It's confusing; it's come too quickly," one Tobin School parent said last week, as he listened to Lannon present the plan. "I don't think it's what anyone wanted."