kill the teacher!
this is a pic or i coulednt do my prank
bring a polished fake knife were it goes in when stabbed.
put some red food coloring in hull of the fake knife.
here is how to do it:
at break try to stay in, if that fails do it in golden time
or were you can do anything. go up to the teacher and use the fake knife on him/her. the food coloring should scare him/her
because it is red for blood. walk away like nothing happened
if you put extra food coloring in it should go on the teachers shirt and nothing will happen...