What was going on when I was born?

Schools Chancellor Nathan Quinones said yesterday that three children had been removed from classes by community school district superintendents this term because of suspicions that boyfriends of the students' mothers had AIDS. The students themselves, he said, had not been reported as having acquired immune deficiency syndrome. He said that in one of the cases, he threatened yesterday to exercise his authority to supersede the district school board unless district officials agreed to permit the 9-year old child to return to school. At 6 P.M., the deadline for the district officials to respond, Mr. Quinones announced he had just been informed that they had agreed to permit the student to return.

International Mikhail S. Gorbachev laid out a formal arms proposal to the United States and offered to make a ''separate agreement'' with France and Britain to halt what he called the ''infernal train'' of the arms race. [Page A1, Column 6.] President Reagan welcomed the change in the Soviet position on arms control outlined in Mikhail S. Gorbachev's speech in Paris. The President called the alterations substantial and said he had no objection to separate negotiations between Moscow and Britain and France. [A1:5.]

Until last month, Canada's highly concentrated banking industry had gone 62 years without a bank failure. But since Sept. 1, two of the country's 14 banks have collapsed, leaving behind a potential Government loss of more than $3 billion (Canadian) and the likelihood of major regulatory changes. And rumors were circulating today in Canada's financial community that a third bank, the Mercantile Bank of Montreal, is in difficulty and could be sold or forced to liquidate in the next week. The problems have been linked to bad loans in the energy field, real estate and other sectors, echoing similar difficulties at banks in Texas, Oklahoma and California.

The largest law firm in Washington, D.C., Covington & Burling, dropped South African Airways as a client last week, only days after a boycott of the firm by law students at Harvard, Yale, New York University and a number of other schools cut into its efforts to recruit new associates. The firm confirmed Wednesday night that ''our relationship with the airline was terminated'' last week, but it gave no reason for the action. The firm denied, however, that the decision to cease representing the state-owned airline, whose litigation and regulatory cases it had handled for 10 to 15 years, had been linked to the boycott. ''The subject is one that we have considered for a long time within our firm,'' said Mark A. Weiss, a Covington & Burling partner and member of its management committee. ''I can tell you that the timing was coincidental.'' Airline officials did not return telephone calls yesterday.

Defense Secretary Caspar W. Weinberger charged today that the Soviet Union had abandoned the idea of ''mutual assured destruction'' that had long been the basis of nuclear deterrence, and had raced ahead with its own antimissile defense program, even as it denounced President Reagan for doing the same. In a speech to the Philadelphia World Affairs Council, a text of which was made public in Washington, Mr. Weinberger said the United States had rejected dependence on arms-control treaties and the threat of mutual destruction as ''the ways of the 60's'' only after the Soviet Union had abandoned them long ago in practice. ''We have learned that the dogma of agreed mutual vulnerability, over the long term, is not a safe guarantee against nuclear war, particularly when the Soviets do not accept it,'' he said. Space-Defense Strategy He defended the United States quest for a way to defend against attacking missiles as the only strategy that can protect America and its allies from nuclear war ''regardless of Soviet activities.''

Mikhail S. Gorbachev laid out a formal arms proposal to the United States today and offered to make a ''separate agreement'' with France and Britain to halt what he called the ''infernal train'' of the arms race. ''It is time to start between us a direct dialogue,'' the Soviet leader said, referring to proposed talks with Britain and France, ''and try to find an acceptable way out through joint effort.'' Mr. Gorbachev, speaking to members of the French National Assembly on the second day of a four-day visit to France, said it was now possible to achieve an agreement on European missiles ''outside of direct connection with the problem of space and strategic arms.'' Linkage of Arms Talks In the past the Soviet Union has insisted that the independent nuclear arsenals of Britain and France be included in any agreement with the United States on missiles based in Europe. The Russians have also insisted that all aspects of arms talks, including space weapons and missiles in Europe, be linked to each other.

LIKE the Pied Piper, Pina Bausch is literally followed by followers - in this case, young dancers pleading to join her West German company. The impact left by the 1984 United States debut of the Pina Bausch Tanztheater Wuppertal, which is appearing at the Brooklyn Academy of Music in a return engagement, has been deeply felt. After ''Kontakthof'' - a work at the academy this weekend that both humorously and mercilessly examines male-female relations - was performed recently in Montreal, two dancers approached Miss Bausch backstage about an audition. Later, a young woman did the same in a hotel restaurant. The demand is so great that the academy has, in fact, arranged for Miss Bausch to hold auditions during the company's run here through Oct. 22. Perhaps there is no greater proof of how successfully Miss Bausch's choreo-graphed theater-pieces can touch people than in this urge to become part of the international and communal troupe she directs from a small industrial West German city. And touching people - sometimes in ways that disturb them deeply - is obviously Miss Bausch's prime concern. ''I want to feel something, as a person,'' she says of her own attitude toward dance-watching, ''I don't want to be bored.'' Feeling, in fact, is paramount in Miss Bausch's work, and nowhere does she experiment with emotions more typically than in her penchant for repeating scenes and gestures - a device that has caused considerable comment.

Scientists say they have discovered the first direct evidence, 65-million-year-old soot, that fire once swept the world and contributed to the mass extinction of dinosaurs and many other forms of life. In a report in the journal Science, published today, chemists of the University of Chicago said the ''surprisingly large amount'' of soot appeared to be worldwide, could have been produced only in flames or hot gases and represented fallout from a dense smoke cloud that must have brought a killing darkness and chill to the world. From the soot residue, found in ancient sediments, the Chicago chemists theorized that the firestorm was ignited by the impact of a huge asteroid or comet. Plants and Animals Died The findings were seen as further evidence supporting the hypothesis, advanced six years ago, that an extraterrestrial object struck the Earth with such violence 65 million years ago that the airborne debris of dust, rock and vapor cast a pall over the world. In the darkness, the theory goes, plants withered, grazing animals starved and the predators that fed on them became extinct, as did more than half of all the plant and animal groups.

As finance ministers from 149 countries start to gather here for the 40th annual meeting of the International Monetary Fund and World Bank, the major topic of conversation is the revised American strategy for fighting the world debt crisis. Turning away from previous support of I.M.F.-imposed austerity programs, the Reagan Administration is now focusing on trade expansion, encouragement of market-oriented policies in debtor countries and mechanisms to get more money to the poorest lands. ''The big message is that we're for growth,'' said one Washington official. ''If you attract capital with pro-investment, pro-market policies, you can soften the harshness of the programs.''

Because of a mechanical error, an article in Metropolitan Report yesterday about Hydro-Quebec utility crews providing help to storm-damaged Connecticut was omitted from some copies and another article, on restoration of electric power to Long Island and Connecticut, appeared twice. Readers wishing copies of the missing article may write to Production Quality Control, The New York Times, 229 West 43d Street, New York, N.Y. 10036.

Companies Revlon agreed to a complicated buyout by Forstmann Little that involves breaking the company into three parts. Revlon said the deal was worth $3 billion, but shareholders will receive only $1.6 billion. The rest reflects what Forstmann Little will get from the sale of Revlon assets and the assumption of debt. Forstmann, joined by Revlon's chairman and other members of management, would retain Revlon's health-care business. [Page D1.]

Ever since a flying sugar maple slammed against the house, taking a bite out of the roof, Audrey Lamborn has been searching for a building contractor and an insurance agent. But six days after Hurricane Gloria, there is still a hole in the roof. And Mrs. Lamborn is still trying to find the people who can put the pieces back together again.