What was going on when I was born?

Thousands of youngsters were turned away from New York City's public schools yesterday because they lacked either proof of immunization against childhood diseases or permission from their parents for the schools to give them the legally required inoculations. The teachers of a school system struggling to reduce its dropout rate found themselves in the awkward position of directing students to leave classes and not to return until they had complied with the law. School officials are hoping that most students barred yesterday will provide the required documents today so that they can be readmitted. They say that the attendance bureau will look into the cases of those who are absent for more than a few days.

The Consumer Price Index, the nation's most widely followed measure of inflation, climbed eight-tenths of 1 percent in August, helped by a moderation in the increase of housing costs, the Labor Department reported today. The results, while containing some mildly unsettling data on food and clothing, were nevertheless broadly in line with the expectations of economists and were regarded as confirmation that the big 1.2 percent jump in July was largely a fluke related to the cost of housing. Consumer prices rose a fu ll 1 percent in the New York-No rtheastern New Jersey area. (Page D6.) ''I think it is a pretty good report,'' Lacy H. Hunt, ch ief economist for the Fidelity Bank of Philadelphia, said of t he national figures. ''Most importantly,'' he added, ''the in flation performance in August is really considerably better than t he eighttenths of 1 percent reported would indicate.'' Despit e the exceptionally high mortgage rates that helped push the mon thly inflation level back to double-digit annual rates during t he latest two months - 15.2 percent in July and 10.6 percent in Augu st - the longer-term downward trend appeared to remain intact.

For the better part of a month, Jack Henry Abbott stayed a step ahead of Federal authorities, who were armed with information from the New York City police as they traced his path. They tracked him from flophouses in the French quarter of New Orleans to bunkhouses in the South Louisiana oilfields before apprehending him yesterday afternoon in a pipeline inspection yard a mile east of here. Mr. Abbott, a convict and author who had been befriended and employed by Norman Mailer, had been on the run since shortly after dawn on July 18, when Richard Adan, a 22-year-old aspiring actor and playwright, was stabbed to death outside the Bini-Bon restaurant at Second Avenue and East Fifth Street in Manhattan, where he worked as a waiter. Late this afternoon, Mr. Abbott, who had been seen arguing with Mr. Adan immediately before his death, was charged by the Manhattan District Attorney's office with murder, and a warrant for his arrest was issued by Judge Jeffrey N. Atlas of Criminal Court. Law enforcement officials said they expected Mr. Abbott to arrive in New York, escorted by Federal marshals, late tomorrow afternoon. He has retain ed Ivan Fisher, a New York criminal defense lawyer.

Home builders, among the leading advocates of the tax-exempt savings certificates created by Congress, appear unlikely to benefit very much from the money that banks will raise from the certificates after they go into effect on Oct.1. Analysts say that very little of the money will be invested directly into home mortgages, although that was one of the the intents of Congress in creating a savings instrument that would provide less costly funds for financial institutions. The analysts see the certificates as being of primary benefit to the balance sheets of the nation's mutual savings banks and savings and loan associations, together known as thrifts. Congress had hoped that the thrift institutions would use the cheaper money from the certificates to finance more mortgages and thus stimulate home construction, now at one of its lowest levels in 35 years. But because much of the flow into the new tax-exempt certificates will merely be transfers into new accounts, bankers forecast, and because the certificates will only be sold for 15 months, the possibility that the money will flow into long-term housing loans is seen as doubtful.

In the News of Music column yesterday, the broadcast date for a complete, 12-hour performance of John Cage's "Empty Words" on WNYC was given incorrectly. The performance will be broadcast tonight starting at 9:30

On Tuesday, New York City's voters went to the polls in a primary election that had been postponed for 12 days by the courts. But the primaries did not include voting for members of the City Council, and that is at the heart of the controversy surrounding the election. When the City Council drew new districts for itself earlier this year - and at the same time increased its membership to 45 from 43 - it began the process that eventually led to intervention by the courts and the United States Justice Department in the city's electoral process. Critics of the redistricting plan charged that it was designed mainly to insure the re-election of incumbent Council members and that it discriminated against the city's black and Hispanic population. Council members did not dispute that their plan may have protected incumbents. But most insisted that their plan had been fair to the city's minority groups. Yesterday, Edward N. Costikyan, the Council'sattorney, held a news conference to discuss the presentation he has made to the Justice Department in defense of the plan. The department will now assess whether the Council's lines violate the Federal Voting Rights Act.

A news analysis yesterday on the examination of Roman Catholic seminaries in the United States incorrectly identified the president of the National Conference of Catholic Bishops. He is Archbishop John R. Roach.

Senior officers of the Army Special Forces permitted one of their staff sergeants to recruit a group of former members of the elite commando troops to train terrorists in Libya four years ago, even though they did not know whether the operation had Government approval, according to several Army officials. The Army later learned, they said, that the operation was not sanctioned by the Central Intelligence Agency or the Defense Department. ''If the operation wasn't run by the United States Government, it should have been,'' said one former commanding officer in the Special Forces, better known as the Green Berets. He added that some Green Beret officers believed the Libyan operation might produce valuable intelligence. Action Outside Usual Channels?

Gen. Wojciech Jaruzelski, the Polish Prime Minister, told Parliament today that he had instructed the army and police to crack down on lawlessness and anti-Soviet activity. He also said the fate of Poland depended ''to a considerable extent'' on the policies to be adopted by Solidarity, the independent labor organization, during the second phase of its national convention, opening Saturday in Gdansk. In the first phase of the convention earlier this month, union delegates angered the Soviet Union by adopting several politicalsounding resolutions, notably one that expressed support for any other independent labor organizations that might arise elsewhere in the Soviet bloc.

IT began one rainy spring day in a little cafe on the Mediterranean. At two tiny square tables in the back sat a woman and four men, busy sipping coffee and kir and speaking in tones that were not meant to be overheard. For two hours they talked and argued and agreed and disagreed. Some took notes, somebody ordered a ham sandwich, many smoked. In the end, amid the muted tensions that inevitably accompany such endeavors, 11 of the 32 movies to be shown at the 19th New York Film Festival, which opens at Lincoln Center tonight, had been chosen. The rest would be selected later, but the tone had been set, the direction established. The first official phase of what could be the film world's most exhaustive scavenger hunt was over.

VIRTUALLY every crammed booth at the third annual Fall Antiques Show has some outsized offering of compelling appeal. If it isn't the size of an object that proves arresting, there is some other unusual quality in the antiques to be viewed at this bazaar - the largest show of Americana in the country - which opened yesterday with 90 dealers at the Passenger Terminal Pi er, 12th Avenue at 54th Street. For some, the unusual quality might be the color-pulsing pattern of aquilt, or the novel shaping of a weathervane, the aristocratic bearing of a kas cupboard or the curious design of a multidrawer table. They'r e all there through Sunday. A Queen Anne chair from Rhode Island with an amazing back, 64 inches from foot to top, is the tallest seat in the show - and one of the more expensive at $9,000. It is on view at the booth of Jill and Edward Abrahams, who also are offering one of the largest toys at the show - a six-foot-long model of a Baltimore fire department engine, complete with side ladders, that priced at $6,000. Larger still is William Greenspon's eight-foot six-inch-high tin man, a 1920's shop figure priced at $17,000. Thereis also a carefully carved alligator, a nine-foot-long reptile with a fish in its mouth, shell eyes and a boat-varnish finish that Jeanne R. Jones will part with for $15,000.

Business economists meeting here said today that their collective opinion had swung in the last two months to predictions of a recession before the end of 1981. In a computer-assisted survey, taken at the annual convention of the National Association of Business Economists, 53 percent of those who participated said the nation's economy was in a recession now or would be before the end of the year. This attitude is a turnaround from results of the association's written survey, taken in July and August, in which more than 60 percent of the economists said there would not be a recession until after the end of 1982. In that survey, only 25 percent saw a recession before the end of the year.