What was going on when I was born?

The president of the New York Power Authority said today that the risk posed by the Indian Point nuclear plants in Westchester County was so small that the reactors should be allowed to operate despite questions about emergency planning. ''Even without prompt evacuation, the plants still would meet the commission's preliminary safety goals,'' the official, Leroy W. Sinclair, said at a hearing conducted by the Nuclear Regulatory Commission. The N.R.C. also heard from officials of Rockland County, across the Hudson River from the plants, and Westchester. Herbert Reisman, the chairman of the Rockland Legislature, said local opposition to the emergency plans was deep-seated. ''These are not antinuclear freaks,'' he said. ''These are tough guys who are used to facing danger every day. I'm talking about the guys that have to go out there: the policemen, firemen, Health Department workers. They said this plan is garbage.''

Children in New York City's public schools are continuing to perform above national norms on reading and mathematics tests, according to statistics released yesterday by the Board of Education. This year, 427,890 students in the city took the reading test and 426,367 were examined in mathematics. The tests were administered to those in grades two through nine. The preliminary results of the examinations, given last month, showed that 55.5 percent of the students tested in reading and 58.1 percent of those tested in mathematics had scored at or above grade level.

The annual meeting of the American Iron and Steel Institute, normally a chummy spring rite for hundreds of the nation's top steel executives, will be remembered this year for its undertone of fractiousness. For the first time in recent memory, delegates to the industry's two-day circling of the wagons at the Waldorf-Astoria agreed, the big issue was the conduct of another steelmaker - the United States Steel Corporation at that. Industry executives reacted with dismay, and outright hostility, to the company's recently announced plan to import up to 3.5 million tons of steel slabs over several years from British Steel. ''It's a step backwards,'' said Frank Luerssen, chairman of the Inland Steel Company, the industry's seventh-largest producer. ''It's counterproductive to our relations with the union.''

Calvin Hampton will give the last of a 13-year-series of free midnight concerts at Calvary Church, Park Avenue South and 21st Street, tonight. Mr. Hampton, who has been Calvary's choir director for 20 years, is ending his affiliation with the church to concentrate on composing and concertizing. One of his specialties is transposing orchestral works for the organ. In tonight's concert, he will play his version of Moussorgsky's ''Pictures at an Exhibition'' - written originally for piano. Also on his program is Mozart's F minor Fantasy. A BROADWAY REOPENING The New Apollo Theater on West 43d Street, dark since ''Fifth of July'' closed in January, reopens tonight at 8 for previews of a comedy, ''The Guys in the Truck,'' starring Elliott Gould as a heavybetting television sports director. Written by Howard Reifsnyder, a former CBS sports producer, the play is a behind-the-scenes look at the people who televise pro football. It's set in a broadcast truck parked under Cleveland Municipal Stadium during a game. Tickets: $17 to to $30. Reservations; 921-8558. Chargit: 944-9300. Ticketron: 977-9020.

Congressional action has cleared the way for creation of a branch of Federal District Court in the center of this Westchester County city, Federal and city officials said today. It will be the first branch in the court's jursidiction, the Southern District of New York, which includes six counties north of New York City. Officials of the court, which is based in Manhattan, said the move was intended to meet the need for more space and to make the court system more convenient for all parties to Federal litigation.

International Unstable global currency rates, according to President Reagan, can be controlled by general economic recovery and reduced inflation. Differences between the United States and France over currency rates are expected to be a major issue at this weekend's seven-nation economic summit meeting in Williamsburg, Va. (Page A1, Col. 6.) The killing of a U.S. military leader in San Salvador Wednesday probably arose from political motives, according to the United States Ambassador. Western and Salvadoran officials differed on whether the assassination of the officer, Lieut. Comdr. Albert A. Schaufelberger 3d, the deputy commander of the United States Military Group there, was carried out by the left, the extreme right or some segment of the Salvadoran security forces unhappy over the level of United States involvement. (A1:1.)

President Reagan, indirectly rebuffing President Francois Mitterrand's proposal for stabilizing exchange rates, said today that the answer to the instability lies in general economic recovery and in conquering inflation. Noting the declines in inflation and in interest rates in the United States and the start of an economic recovery, Mr. Reagan said: ''I think the relationship between the currencies must be resolved by this general recovery and by more stability and more closeness as to inflation rates worldwide.'' Then, apparently alluding to the French inflation rate, which was 11 percent last year, nearly double the American rate of 5.9 percent, Mr. Reagan added, ''Currencies are going to be stabilized when we conquer inflation.'' Two weeks ago, Mr. Mitterrand called for an international monetary conference to move back toward fixed exchange rates, which were abandoned a decade ago. He contended that high American interest rates were draining investment capital from France, thus stalling French economic recovery.

The chairman of the National Association for the Advancement of Colored People reinstated Benjamin L. Hooks as executive director yesterday, eight days after she suspended him. In a statement released at N.A.A.C.P. headquarters in Brooklyn, the chairman, Margaret Bush Wilson said the dispute over management of the organization that led to the suspension had been resolved. ''No useful purpose would be served'' by continuing the suspension, the statement said without elaboration. It said that Mrs. Wilson had notified Mr. Hooks that he should return to his post today and that she would explain the reasons for her action at a special board meeting she scheduled for June 11.

Mannesmann A.G., a maker of steel products, said today that it was holding talks with the Soviet Union on the sale of strip-mining and coal-processing equipment to develop huge reserves in southern Siberia. The project would match in scope the contracts signed with European nations to provide equipment to help build a Soviet pipeline to carry natural gas from Siberia to Western Europe. Soviet officials have said that contracts for the coal plants and mining equipment could total $16.5 billion, spread over the rest of this century, according to German analysts. Antagonism Over Pipeline The gas pipeline was vehemently opposed by the Reagan Administration, which argued that Western Europe should not become dependent on Soviet energy supplies and that the Russians could use hard-currency earnings from the gas sales for military activities. But the fuel from the coal project would be used within the Soviet Union, and therefore Washington would probably not object to the German involvement, a United States Government official said today in Washington.

''There comes a time in the life of every man and any city when change is appropriate.

Governor Kean presented plans yesterday to build a state prison for 1,000 inmates on a vacant plot north of Newark International Airport. Appearing with Mayor Kenneth A. Gibson in Newark's City Hall, Mr. Kean described the $100 million prison as a major part of his yearold plan to ease severe overcrowding in the state's medium- and maximum-security prisons. As of a month ago, according to the Department of Corrections, these prisons contained 8,159 inmates in facilities designed to hold 7,166. Some inmates are being housed in prison chapels, gymnasiums and classrooms. There are also 1,300 in county jails, straining their capacities.

The Israeli and Syrian Armies, facing each other across the ravines and plains of eastern Lebanon, are busy fortifying their positions by strengthening earthworks, reinforcing bunkers and building access roads. From the Israeli side of the uneasy, unmarked cease-fire line, there is no evidence that either Syrian or Israeli troops are preparing to leave. On the contrary, they are digging in and waiting in case the diplomatic tension flares into fighting. This week the Syrians fired missiles at an Israeli helicopter and a reconnaissance aircraft, drawing warnings from the Israeli Army about violating the cease-fire.