What we need to ask is how many violent attacks are there on schools in this country with guns - or knives, hammers, or anything else. The answer is very few.
If you take guns out of the equation by limiting the general public's access to them, you lower the profile of schools as targets for attack.
In the US at the moment it seems that every mentally ill disaffected youth/man, who wants to get even with - something - a school, society, life in general etc etc knows that he can go out in a blaze of glory and international notice by shooting up a school and killing as many children as possible. Schools are, as a a result number 1 target.
In this country guns are difficult to acquire - especially if you are a loner, as so most school shooters(US) and knife attackers (UK) are , and while there have been a number of knife attacks, as a general rule, victims are far fewer.