Unfortunately, most gaming sites have been blocked by your school network administrator with reason feared disrupt students' learning process. It is true that, if uncontrolled will of course interfere with student learning, but if played only moments of leisure and in the not too long I guess it does not matter. But it will certainly complicate its own network administrator in setting their firewall rules. But you need not worry, we provide the following list of online unblocked games at school for you that you can play from your school.
Panic attack killing zombie - zombie game genre and this shooting you can play here: http://games.mochiads.com/c/g/panic-killing-zombie-attack/panic% 20killing% 20mochi% 20en.swf
zombie guard - another zombie game genre themed tower defense you can play here
and many more list unblocked games at school you can play, please search with the keyword you want to play games in the search field.