I already speak a second language - pig latin! Never had one lesson, either!
Seriously though - if you are taking German, I would suggest a book called English Grammer for Students of German. I'll look up the author later and let you know the name. It helped me enormously in my classes. My main problem with German grammer was that I didn't know English grammer.
Seriously. Never had to diagram 1 sentence in school. Ever.
Love those public schools!!!