While I use McVeigh as an example, truth be told, his level of skill is beyond what a regular civilian could be expected to muster. He was an exceptional private ordinance man. The bomb he built was actually really impressive for a home job. Part of why he didn't catch on was the attack location. In order to put it into the minds of the bad guys, it has to be more relateable. You need to normalize the experience more. When an Ex-Military Guy goes and attacks a Government building on a epic scale, people just go

Now if a high school drop out blows up a Walmart, there is a small fucked of percentage of the population that reads, "That could be me, I could do that." The more your broadcast that thing, the more likely it is to stick.
Here is a show of a school more interested in the right approach.
https://www.abqjournal.com/1145498/aztec-high-school-plans-walk-up-in-wake-of-gun-violence.html
They want to attack this as a social issue. Kids talking about bringing in odd kids out of the cold, making friends and including outsiders. The only real way to solve the school murders problem is by embracing the Unity in Community.
The school violence problem will never be solved until we discard this new divisive model of American politics and embrace our neighbors across the aisle. The us vs. them mentality of our nation must be destroyed and we have to go back to the old American idea of standing together against the rest of the world, not aligned against one another.