Depends on what makes up the data in your chart.
Most likely it contains bogus school shootings, as previously uncovered the alarming statistics being used by the left included instances where students brought empty guns (no shooting)...one was an accidental shot by a police officer during a demonstration, several instances of students who brought to school BB Buns and air pistols....all were counted as a School shooting event.
Actually it doesnt depend on it for the point I was making. I doubt there is any entirely accurate data but we all know something has changed. Yeah I read that article wherein for example a student criminal justice class meeting off campus accidentally discharged a weapon they were being trained on and those anti-gun nutjobs counted it as a school shooting.
I dont know how accurate the chart is. I got it from wikipedia. But I feel like the trend is accurate. even if it ,might not be scientifically rigorous in its data. I am open to correction on it.
File:School shooting deaths injuries by decade.png - Wikipedia
But my point is, whether the rate went up or down the 2nd amendment didnt change. Look to another variable for any uptick in violence. I myself lay the blame on the liberal destruction of our culture.