For three months negotiations had been growing more heated but not more successful as Cambridge's teachers and school committee attempted to hammer out a new contract.

Facing already large tax increases, the school committee was unwilling to grant large pay increases this year. And faced with double-digit inflation, the Cambridge Teachers Association (CTA) was demanding a big hike; last week, the membership even authorized a strike if the school committee didn't give in.

So when an independent mediator finally suggested terms for an agreement at 1:10 a.m. Friday, it seemed unlikely he'd be able to bring the two sides together. An hour later, though, representatives of the two sides were shaking hands.

The surprise agreement attested both to the weariness of the negotiators and the mediator's skill.

"Both sides knew bargaining had gone on a long time, and neither wanted to prolong it," Cambridge mayor Francis H Duehay '55, who is also chairman of the school committee, said yesterday.

"But without the mediator, I think we would have been out on the bricks this morning," Roland LaChance, president of the CTA, said yesterday.

Both sides concede the settlement was very much a compromise. The salary issue proved hardest to settle; the mediator's terms allowed the school committee to raise pay only an average of $1000 this year, but gave the CTA a hefty 8.25-per-cent raise in the second year of the pact.

"Salary will be the only item some of our people will object to, and there are some pockets of resistance already," LaChance said, but he added he expected the membership to ratify the pact late this month or early next.

"The School Committee made no inroads into our present contract, and in this day and age that's quite a feat," LaChance said.