"Over 2,140 others have been injured. The actual numbers are likely to be much higher," Relano said in a statement published on UNICEF website.
He added that some 2,000 schools were destroyed, damaged or used for military purposes or as shelters for displaced families.
"Schools should be zones of peace at all times, a sanctuary where children can learn, grow, play and be safe. Children should never risk their lives only to attend school," Relano underlined, adding that UNICEF called on all parties to the conflict to follow their obligations under international humanitarian law and stop attacks on civilian infrastructure, including schools.
Since March 2015, the Saudi-led coalition of mostly Persian Gulf countries has been carrying out airstrikes against the Houthis at Hadi's request.