I think maybe we are confusing the word "memoir" and the word "biography" and "autobiography". A "memoir" is not the same thing as an "autobiography".

I agree that memoirs, bios, and autobios can all be useful reading, along with other forms of books. A memoir is only so useful as the author's POV is useful in teaching young people. A memoir written by a narcissistic, self-centered person is not a good teaching tool, IMO. A good biography of a successful person such as a political figure or someone who overcame diversity in life, might be useful school reading. I'm not going to say it is more important than the large amount of mandatory reading kids already have.