The leader of the United Nations’ agency for Palestinian refugees on Saturday condemned the Israeli strike on a school in Gaza, which Palestinian authorities said left up to 100 people dead. Philippe Lazzarini, the head of the United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA), said the incident represented “another day of horror in [Gaza].” “The unbearable cannot become the norm,” he added. Lazzarini said all parties to the conflict in Gaza “must protect civilians and civilian infrastructure at all times” and refrain from using “schools and other civilian f…