Outside of those nine spells I don’t have time to learn anything else, like, for example, the entire first year curriculum, and truth be told I still don’t see the point. The spells I did learn were cherry picked to ensure my survival. Spending time learning the useless spells taught in first year would only advance my grades, which would not be any good to me if I was dead or crippled in an "unfortunate accident’. I am not safe in a society that is so utterly indifferent to me due to blood status. I had some protection due to how close I am to Holly, but in other circumstances the best I could hope for would be a distant, "oh how sad’, over my mudblood corpse, if that.