Palestinian school boys drink iced juice as they sit on a damaged wall of a school in Gaza City's Shijaiyah neighborhood, Sunday, Sept. 14, 2014 (Photo: AP)

Palestinian school girls do their morning exercise in a damaged school during the first day of school, in Gaza City's Shijaiyah neighborhood, Sunday, Sept. 14, 2014 (Photo: AP)

Palestinian school girls do the morning exercise in a damaged school during the first day of school, in Gaza City's Shijaiyah neighborhood, Sunday, Sept. 14, 2014 (Photo: AP)

Palestinian school children walk past a destroyed building during the first day of school, in Gaza City's Shijaiyah neighborhood, Sunday, Sept. 14, 2014 (Photo: AP)

Palestinian school girls sit in their classroom, as a paper with Arabic wring that reads," martyr Ghada Sobhi Ayyad," the name of a student who was killed during the war , is placed at her empty seat in a classroom at a school in Gaza City's Shijaiyah neighborhood, Sunday, Sept. 14, 2014 (Photo: AP)

Palestinian students play inside their school that witnesses said was shelled by Israel during its offensive, on the first day of the new school year in the east of Gaza City September 14, 2014 (Photo: Reuters)

The empty chair of student Najeah al-Helo, 14, who was killed during the Israeli offensive, is seen inside a class on the first day of the new school year in the east of Gaza City September 14, 2014 (Photo: Reuters)

Palestinian students sit inside their school that witnesses said was shelled by Israel during its offensive, on the first day of the new school year in the east of Gaza City September 14, 2014 (Photo: Reuters)

Palestinian school girls walk to their classrooms during the first day of school, in Gaza City's Shijaiyah neighborhood, Sunday, Sept. 14, 2014 (Photo: AP)