Jerusalem ? Large numbers of students in U.N.-run schools in Gaza have flunked achievement tests in math and Arabic, the agency said Thursday, attributing the poor showing to violence, overcrowding and poverty.

More than two-thirds of students in grades four through nine failed math, and more than one-third did poorly in Arabic, said the U.N. Relief and Works Agency, which runs schools for more than half a million children of Palestinian refugees across the Arab world. Ninety percent of Gaza sixth-graders failed the math test, UNRWA said.

In contrast, Palestinian students at U.N. schools in Lebanon, Syria and Jordan are doing better than their counterparts in government schools, indicating that a stable environment is key to learning, UNRWA said.