In most of the european world, its 12 years-ish for schooling. (before college or university)
Its a common enough idiom.

And no, simple biology / chemistry is completely wrong. We will soon know that.
Louis Pasteur knew this and lied so that he could make lots of money selling medicine.

If we had accurate enough tests we would find that every disease exists in every person.
So, why doesn't every person have every illness?

Within 10 years, all of the medical books will be rewritten.
And that is just with the stuff i know now.
I am certain far more will be learned in the near future.

Defending oneself is the most important thing.
If someone insists on trespassing, if someone fails to respect boundaries,
then all means to stop them should be applied.
If lesser means fail, then shooting them is appropriate and necessary.

You wouldn't allow a murderer (who just happened to not be murdering right now) into your living space would you?