Although Kielkucki denied that the picket line was timed to coincide with the pope's visit, he said the striking teachers decided to set up picket lines at only one school on Friday - Cathedral High School on 56th Street and First Avenue.
The pope was starting his three-day New York visit at the United Nations, and also was scheduled on Friday to visit a synagogue and lead a prayer service with leaders from other Christian denominations at St. Joseph's Church in Manhattan.
The teachers planned to picket until 1 p.m. along First Avenue, between the school and the New York Catholic Center. Afterward, the union had a meeting scheduled with the Archdiocese of New York, Kielkucki said.
A call for comment to the archdiocese was not immediately returned.
The teachers first walked out Tuesday in a dispute over wages, health premiums and pensions.
Some schools have had to close early because of the strike. The union represents 450 teachers at 10 schools in New York City and its northern suburbs.