It’s only about one per week, if you average it out over the whole year, including when there is no school.
2022 had 51: https://www.edweek.org/leadership/school-shootings-this-year-how-many-and-where/2022/01

If you are just talking about “mass shooting” events, it’s closer to 2 events per day in the USA.
https://en.wikipedia.org/wiki/List_of_mass_shootings_in_the_United_States_in_2023#List