RAFAH, Gaza Strip—Huddled in classrooms and crouching under tarps slung up in the courtyard, Palestinians seeking refuge from the fighting raging in Gaza have crowded into a United Nations-run school here near the Egyptian border.

The U.N. Relief and Works Agency for Palestine Refugees runs 183 schools in the Gaza Strip, most of which have been pressed into service as shelters. The agency, which also runs bakeries and clinics and provides financial aid, has been central to life in the Palestinian enclave for more than 70 years.