April 26, 1981

The official Soviet press agency warned today that the Polish Communist Party was being threatened from within by ''revisionism'' - one of the gravest ideological heresies in the eyes of the Soviet leadership. It was the first time since the labor and social crisis erupted in Poland nine months ago that the Soviet press had raised such a grave charge - one that has historically been leveled by the Kremlin against its major adversaries in the Communist movement. It was used in 1968 before the Soviet-bloc's invasion of Czechoslovakia. In Warsaw, the Government and the Solidarity trade union movement began talks on a variety of persisting issues. The talks, conducted on national and local levels, were the first since last fall not to be overshadowed by strikes threats. (Page 14.)

For 12 years, Protestant and Roman Catholic militants have tried to determine the fate of Northern Ireland by killing each other. Bobby Sands is trying by killing himself. Mr. Sands, ''camp commander'' of Irish Republican Army inmates at Maze Prison outside Belfast, has now refused all food for 56 days, three days longer than seven prisoners who gave up an earlier fast in December. up an earlier fast in December. His sight and hearing failing, he was given the last rites eight days ago.

YEAR-OLD Laverne Joseph had been out of school for four years when she showed up one day recently at a New York City public schools ''outreach center'' for dropouts. In as nonthreatening a tone as he could muster, Edward Phelps, an intake counselor, asked her quietly, ''What went wrong?'' The youth responded with a story that has become increasingly familiar to school officials. She had had trouble with a teacher who ''blamed me for things I didn't do,'' so she began casually cutting her classes at Adlai E. Stevenson High School. Soon she was hanging around with friends who were also on the verge of dropping out, which led to a string of low-paying and unrewarding jobs, as a nurse's aide and a locker-room attendant at Orchard Beach, and, finally, a decision to try for a high-school-equivalency diploma. ''When I didn't work I would look at soap operas, but that got boring,'' she explained.

The Administration's first 100 days expire this week, and the period has attracted punditry. Actually, the next three weeks or so are taking shape as make or break for the Reagan economic program.

The measure under consideration was a bill declaring that human life begins at conception, thus making abortion equivalent to murder and criminally punishable. The sessions, held in a packed Senate hearing room over two days last week, were as highly charged as the issue itself. All five witnesses called by a Senate Judiciary subcommittee on the first day testified that life begins at conception. Prof. Hymie Gordon, chairman of the Department of Medical Genetics at the Mayo Clinic in Rochester, Minn., said this was ''an established fact.'' Dr. Jerome Lejeune, professor of fundamental genetics at the University of Rene Descartes in Paris, compared the fertilized egg to Tom Thumb or an astronaut. Dr. Micheline Matthews-Roth said ''It is scientifically correct to say that an individual human life begins at conception, when egg and sperm join to form the zygote, and that this developing human always is a member of our species in all stages of life.''