What was going on when I was born?

WHEN the opening bell rang at the 55th Street School in Milwaukee one day last week, Linda Martinez greeted her kindergarten class with the words, ''Como esta usted?'' Jonette Pickett and the 21 other 5-year-olds replied in unison, ''Muy bien, gracias,'' and when the teacher read out their names each one replied, ''Presente.'' Then they picked up their ''lapices'' and went to work. Jonette and his classmates all come from English-speaking homes, but they are going to school in Spanish as part of a special program designed to make them thoroughly bilingual by sixth grade. Immersion programs like the one at the 55th Street School are the exception, but they are indicative of a growing interest among parents, teachers and researchers across the country in starting to teach foreign languages at the primary school level.

President Reagan has authorized ''aggressive self-defense'' tactics to protect the Marines in Lebanon and is consulting with Congress on a resolution to approve a continuing American military presence there, Administration officials said today. The officials said ''aggressive tactics'' meant the use of naval planes and guns, if necessary, to protect the Marine force that has been under fire at Beirut's International Airport. In the consultations with Congress, James A. Baker 3d, the White House chief of staff, met today with the House Speaker, Thomas P. O'Neill Jr., to marshal support for a resolution. Mr. Baker was told the President should seek formal backing for American military involvement in Lebanon under the War Powers Resolution of 1973. O'Neill Warns the Syrians ''We want to work together with the White House,'' Speaker O'Neill said later. ''If Syria thinks America is divided and it can wait around until we pull out, they are wrong.''

SCIENTISTS who study biology at its most basic level are in the midst of a crescendo of new discoveries that seem to be unraveling of the mystery of the cancer process. In the last few months, they have added to the list of known human cancer genes, identified new significance in the breakage and rearrangement of chromosomes, begun to see the function of cancer genes' counterparts in the normal body, and identified a two-stage sequence in which two cancer genes of different classes act in step to produce a malignancy. So fast and furious is the pace of discovery that some experts say informally that more has probably been learned in the past few years than in the previous quarter century. ''With the new molecular tools, so many things are just coming together,'' said Dr. George F, Vande Woude of the National Cancer Institute, one of the experts in the field. Most of this increasing wealth of knowledge has to do with the genes, the basic hereditary messages carried in the form of DNA (deoxyribonucleic acid) in all living cells, and with the chromosomes, the tiny threadlike structures that carry those genes somewhat like beads on a string.

A report Friday in the Briefing column of the Washington Talk page gave incorrect information on obtaining the Almanac of American Politics, 1984 edition. It is available (by mail or in person) only at the Washington office of The National Journal, 1730 M Street N.W., Washington, D.C. 20036. The price is $35 for hardcover, $22.50 for paperback.

From the time Congress recessed last month until its return yesterday, New York's two Senators had remained hard at work, each in his own fashion. Daniel Patrick Moynihan was holed up in a former one-room schoolhouse near his farm at Pindars Corners in Delaware County, writing a book on such issues as Social Security and the MX missile. Alfonse M. D'Amato spent the recess as if he were running for re-election - now. His term will expire in 1986. He held news conferences and issued statements on credit-card fraud, lost revenue from state gasoline taxes, narcotics, the Long Island Lighting Company's Shoreham nuclear power plant, the tentative assignment of a naval force to New York Harbor, health care, and Federal loans to companies in the garment district.

The Soviet Union today vetoed a resolution by the Security Council that deplored the Russians' destruction of a South Korean airliner on Sept. 1. Nine nations, a bare minimum required to adopt a resolution, voted for the document. Poland joined the Soviet Union in voting against it. Four nations - China, Nicaragua, Zimbabwe and Guyana - abstained, thus weakening the United States' attempt to demonstrate that most of the world condemned the Soviet deed.

Almost three weeks before the final major step in the deregulation of interest rates, competition for consumer deposits is heating up. Already, Citibank and the Dollar-Dry Dock Savings Bank are running newspaper advertisements seeking to lure deposits into accounts that will become available Oct. 1, and other banks are likely to be drawn into the fray. For individuals, the interest-rate war could be a boon, but it could be extremely costly for the banks. Dollar-Dry Dock is promising to pay over a percentage point more on its one-year government-insured C.D.'s than investors could have obtained yesterday on a one-year Treasury bill. And still, William J. Heron, a Citibank senior vice president, says ''that's not a staggering rate.''

A New York State inquiry into outside legal fees paid by the Metropolitan Transportation Authority has led to criticism of the agency for failure to require a detailed accounting of the billings. The investigation, by the Inspector General of the M.T.A., Sidney Schwartz, found some discrepancies among nearly $2 million in billings by the firm of Davis Polk & Wardwell, which has represented the agency in labor negotiations. The discrepancies emerged when Mr. Schwartz asked the firm to turn over documentation that the M.T.A. had never requested. Lawyers from the Manhattan-based firm, one of the nation's largest, said that it had provided time sheets and other records to back up the bulk of the billings but that some minor ''clerical errors'' had inadvertently been made.

An article in Metropolitan Report yesterday about New York State's new law requiring deposits on beverage containers gave an incorrect telephone number for inquiries. The number, starting tomorrow, will be 267-9800.

Stock prices fell yesterday in heavy trading after an explosive early rally based on hopes of lower interest rates evaporated. Traders cited rumors, later denied, about errors in Friday's money supply figures, as well as underlying caution. At the conclusion of trading, the Dow Jones industrial average was down 10.67 points, to 1,229.07, after having been ahead almost 18 points in the first half-hour of trading. At that time, it exceeded the record close in the key barometer of 1,248.30, set on June 6, by almost 9 points. The Dow ended at 1,239.74 on Friday.

When Hurricane Alicia ripped through Houston last month, it knocked out service of the city's new cable television system for a week. That was just one of a series of devastations to the Warner Amex system and, in its customers' view, the most forgivable; the other disasters have all been man-made. ''If I were God,'' said Drew Lewis, chairman and chief executive officer of Warner Amex Cable Communications, in an interview last week, ''I wouldn't have any problems.'' As it is, however, the former Transportation Secretary has problems aplenty. And while Mr. Lewis and many analysts believe the long-term prognosis is favorable, the troubles of Warner Amex, the joint venture by Warner Communications and American Express, are immense.

The new public-school year begins today in New York City, with more money to spend, expectations of more children to spend it on and a new Schools Chancellor committed to new ideas. The city's nearly one million schoolchildren file back to classes at a time of national focus on improving American education - a new emphasis so intense that teachers and school officials think it will help the largest public school system in the country by riveting attention on its many problems. Those problems range from a high- school dropout rate of more than 45 percent to a steadily increasing population of handicapped children in need of special training and attention. All-Day Kindergarten Due As he begins his first full school year as Chancellor, Anthony J. Alvarado has made the solution of these two problems his top priority. Another matter he is giving major attention is the start of the first citywide all-day kindergarten program.