In my school, I'm taught about how to use the variance, expected rate of return, beta coefficients, to determine if investing in the company is a good thing. Is this information usable out of school?

These are the fundamental guidelines of analysing a stock's intrinsic value from a theory/academic perspective, so of cos there's some value in using it in real-life stock analysis & picking.

But how well you use these 'tools" is ultimately dependent on the user itself

Absolutely. You'll most likely be investing yourself and risk indicators are important factors when deciding what and how much to invest in.