The Israeli answer for the Ma’alot school massacre was not to order the posting on Gun Free Zone signs but to harden schools, post soldiers with rifles and arm teachers and school workers.
Have assholes tried to attack Israeli schools after that? Yes, but rather few so unsuccessfully that pretty much no idiot tries anymore.
Here in the US, we forbid access to schools to those who can answer to the threat and assure parents that their kids will be “protected” by cowards with a pension and a badge.