Shouldn't there be metal detectors at every school and major facility to prevent mass shootings?

Definitely/

What makes sense is to look at where there are fewer or no shootings and see what they might be doing better, then emulate that. We can start with looking across the USA, and then look at the rest of the world.

The researchers identified several factors that were associated with a lower risk of school shootings. They found that the number of school shootings was lower in states that had:
- Mandatory background checks for gun and ammunition purchases.
- Higher spending on mental health.
- Higher spending on K-12 education.
https://www.cbsnews.com/news/school-shootings-states-gun-background-checks-study/

Thirty-nine states had at least one shooting, 34 had less than ten; Florida (14), Georgia (15), North Carolina (12), Tennessee (10), and Texas (14) had the most. A diverse group of states including New York, New Jersey, West Virginia, Wyoming, and seven others didn’t have any… States with higher spending on education and mental health showed lower shooting rates, as did states with stronger background-check gun laws and a greater concentration of people living in urban areas.
https://www.thecut.com/2016/12/what-states-with-the-most-school-shootings-have-in-common.html

Here is a map showing the number of school shootings per state just in 2018:
https://www.wcpo.com/news/national/school-shootings-in-us-when-where-each-shooting-has-occurred-in-2018

Wouldn’t that infringe on a child’s right to carry guns?

In war zones, you usually need to go through a metal detector to get into a school, bar or department store. And the police randomly block off both ends of a street and check every person to see if he is carrying a weapon and has a permit for it. If we get to that point, I'm sure it will happen.

There is a high school in Minneapolis on 50th street south where that never worked in the slightest. Guns still got into that school all the time, those sneaky little shirts without the r.

Why is the solution of school shooting always the school.

My daughter school, there only one door you can enter.
There are cameras inside and outside.
There are school safety officers.
There is a police officer at every school.
Bullet proof glass.

So now instead of looking at guns, you want to put in metal detectors.
When beside schools, will you look at parents and guns.

Yes. And a security guards. Whatever it takes to keep the kids safe.

If they remain gun-free zones, yes, that only makes sense since doing nothing changes nothing.

Many schools have them. They are obviously not working well.