Still not sure what purpose the phone call warnings do, other than just wrecking property for the sake of it - I suppose it's a carry on to the policy of demolishing suicide bombers' home. Rather bizarre form of punishment, rather counter-productive (though one could argue it fulfills a deeper purpose).
Not sure where schools fit in the target classification scheme, but they hit another today, whoops.
UNRWA also made a statement about the previous attack - http://www.unrwa.org/newsroom/official-statements/unrwa-strongly-condemns-israeli-shelling-its-school-gaza-serious