atheism can & should not be taught, whereas the deliberate & purposeful use of one's own brain should. sadly doesn't really happen in our world.

I was never taught atheism. I was born with it. Never learned it. Been second nature. Catholics couldn't remove it. Not a single teaching.

I think the idea of atheism should be taught just so people are less ignorant.

You cannot teach atheism per se, as it is merely a response to the theist claim that a god/s exists.

What can be taught is critical thinking, research methodology and how to apply the scientific method in everyday life.
This may help conclude that atheism is the only rational conclusion given the (lack of) evidence, but more importantly, will give important life skills to check claims of advertisers, analyse the spin from politicians and ask themselves 'is this news fake?'

I don't think any religion or non-beliefs should be actually taught but mentioned in history correctly.

The primary focus should be not only to define atheism, but to dispel the Illusion that Christianity is directly associated with nationalism and atheism is directly associated with anarchy.

Atheism shouldn't be taught to anyone. It's not a thing, but a lack thereof. Religions are by-products of people's refusal to accept reality. If you teach anything in reference to atheism, it should be a very small portion within a Mythology 101 class.

Atheism is negative space. Its only about what isn't and has nothing to do with what is. I do not believe in ghosts. That does not mean that I belong to some religious group that meets on Tuesdays to discuss the wonders of a ghost-free world.