September 3, 1984

New York City's public-school system opens this week with two new high schools, $215 million more to spend than last year, a Chancellor who is still in his rookie year and some new teachers who have never taken an education course. But for the city's 936,800 students, the novelties will mean little next to the verities of a first day of school. Most students will probably once again feel that keen mingling of eagerness and anxiety that September evokes. Many teachers, too, will face the clutching sensation of meeting all those new faces - students who could make their year an agony or could provide that deep gratification of having touched a young soul that is so special to the profession.

The Central Intelligence Agency believes two of the men killed when Nicaragua shot down a rebel helicopter Saturday were American mercenaries, Senator Daniel Patrick Moynihan said today. Mr. Moynihan, a New York Democrat who is vice chairman of the Senate Select Committee on Intelligence, said the C.I.A. had told him that the two were not directly or indirectly associated with the agency, which has supported the Nicaraguan rebels since 1981. Mr. Moynihan said he had been told that the helicopter was on a reconnaissance mission after a rebel ground attack on a Nicaraguan military outpost. There have previously been no known American deaths in Nicaragua associated with the three-year-old rebel fight against the Sandinista Government. A primary concern in Congress about American support for the rebels has been the possibility that C.I.A. employees or other Americans would become involved in the fighting. Some members of Congress have warned that the loss of American lives in the conflict could draw the United States into a more direct and extensive military involvement. The Reagan Administration, partly in response to these concerns, has a standing policy that American Government employees, or anyone working on contract for the Government, shall not take part in any activities inside Nicaragua.

Under a steady downpour and the watchful eye of hundreds of armed soldiers and policemen, tens of thousands of Sikhs jammed a shrine here today for an anti-Government rally at which religious leaders called for a mass march to liberate their holiest site from the army occupation. Thrusting their arms into the air, the Sikhs also shouted their approval for a merger of conflicting Sikh political factions into a unified party, the Akali Dal. The meeting here in Punjab state, described as a world Sikh convention, was designed to ratify a broad anti- Government program that many here believe could lead to sharper confrontations with supporters of Prime Minister Indira Gandhi. In June, Mrs. Gandhi ordered an army assault on the Golden Temple, the Sikhs' holiest shrine, to dislodge a group of Sikh militants.

The bus left Georgia early Saturday morning, carrying 40 people headed to New York City to help rehabilitate a building on the Lower East Side. By late afternoon, appetites were growing. ''Jimmy, can you pass the cookies?'' asked Betty Pope. The man with the pink sweatshirt wrapped around his shoulders turned in the narrow seat and handed over a box of homemade pecan crunchies, not without stopping to take one for himself. ''Thank you, Mr. President,'' Mrs. Pope said.

The President's advisers say he intends to tone down his campaign attacks and shift to positive themes. Page 9. MINNEAPOLIS, Sept. 2 - Walter F. Mondale charged today that the Republicans had ''raised doubts whether they respect the wall our founders placed between government and religion.'' In a free-swinging five-minute radio speech broadcast nationwide, the Democratic Presidential nominee warned that mixing religion and politics ''will corrupt our faith and divide our nation.''