Lots. No more statistically than there are today. In fact, crime in this country is at historic lows and mass shootings have been flat for years. The only reason it seems more common is because of the 24 hour news cycle/Facebook/Twitterverse.
Do you have statistics?
I see that there have always been school shootings. But my impression is earlier the body counts were less: one or two per incident.
It may not just be that these incidents are reported more, but that the publicity encourages higher body counts.
There are stats and lists all over the place. There’s no upward trend in school shootings, the deadliest school killing is still the 1927 Michigan school bombing, and as far as safety is concerned, a school is still one of the statistically safest places a child can be.