Tirym

I am STRUGGLING to find some serious online schooling... even if it's not schooling: it would be enough for me to have myself tested. ( I can study all alone )

Sadly the University of London's distant learning courses are few and mostly devoid of strictly scientific subjects ( math being the only option ) and, as Marat said,

there are lots of "diploma mills" out there and I'm not sure how to verify their credibility / quality.

I wonder if there is any pure-testing facilities... like those for languages ( british council, Goethe Institut etc. ).