Israel summer programs, through which several thousand American high school and college students spend time in the country, are drawing up contingency plans in response to the violence.

One program, Birthright Israel, which has sent more than 100,000 Jewish young adults on free, 10-day trips to the Jewish state during the past six years, has revised travel itineraries but has not canceled any of its summer tours in light of the escalating violence.

About 1,000 Birthright participants from around the world are now in Israel, and another 100 people are slated to arrive today. A Birthright spokesman, Gidi Mark, said tour groups would remain south of Haifa, and planned trips to the Galilee Sea or the Golan Heights region in northern Israel have been called off. As expected, some of those enrolled have withdrawn in recent days, but the cancellation rate has varied widely, Mr. Mark said. “We don’t know why, in one group 20 out of 40 come, and in another 32 out of 40 come,” he said.

Four siblings from Sheepshead Bay, Brooklyn, Mazal, Zelman, Michael, and Levi Agazarova, arrived in Israel yesterday in an 18-person Birthright group.

“We were a little nervous,” Mazal Agazarova, 26, said. “You never know what’s going to happen anywhere. We’re from New York, and any day could be another 9/11.”

Speaking by telephone from Tel Aviv, Ms. Agazarova said her parents were hesitant to let all of their children travel to Israel, but did not forbid them to go. “It sounds more scary than when you’re here,” she said. “Do we sense danger? Yes. Do we sense it as much as we did from New York? No.”

But about 30 college students on another Birthright trip, organized by Hillel: The Foundation for Jewish Campus Life, spent part of the Jewish Sabbath Saturday in a bomb shelter after four rockets fired from Lebanon hit the northern city of Tiberias, where the group was staying. Even so, 13 of the participants celebrated their bar and bat mitzvahs over the weekend, according to a Hillel spokesman, Jeffrey Rubin.

Mr. Rubin’s own 16-year-old son is traveling with his Jewish youth group in Israel, and will return to Baltimore on Tuesday – five days ahead of schedule.

He said it was premature to predict whether American universities would suspend their study abroad programs in Israel, as dozens did during the second intifada. Several schools only recently reinstated such programs.

As of yesterday afternoon, Israel-based high school and pre-college summer programs organized by the youth divisions of the Orthodox Union, the United Synagogue of Conservative Judaism, and the Union for Reform Judaism, in addition to the Young Judea course run by the Zionist movement Hadassah, had not been canceled. The respective groups had corresponded with parents, saying their children’s safety was the top priority, and in some cases informing them of canceled excursions to northern Israel.

Last week, the Jewish Agency for Israel transported about 150 mostly young Americans and other foreign nationals who had been doing internships or volunteering in northern Israel to a youth village south of Jerusalem. “All of the parents have been very worried,” the agency’s director of the Israel Program Center, Ilya Sandler, said. “We told them that they were all safe, and if there was any kind of serious danger, we’d put them on an airplane and bring them home.”

As of yesterday, he knew of only a few people who had planned to return to America.

In nearby Lebanon, which attracts far fewer American summer students, officials at the American University in Beirut – the city that has borne the brunt of Israel’s airstrikes – were urging students to stay on campus, a school spokeswoman, Ada Porter, said. “For the moment, they’re staying in dorms,” she said, noting that there were about 40 Americans now studying at the school. “We’re staying in constant contact with parents and students, and trying to keep them as reassured as possible.”

She said the school was in contact with the State Department about a possible evacuation to nearby Cyprus.