Well, if you have the raw talent.
I've heard of a girl who obtained 48 by only writing essays for her school assessments throughout the year.
Such cases are extremely rare though.
I can relate strongly to this. I probably only wrote a grand total of 10 essays for English throughout the year - one or two as practice before each SAC. I didn't particularly work hard in English (well at least compared to Chemistry, and Physics, I did very little) - would estimate that I spent 2 hours a fortnight on it outside of school time. English, by and large, is a subject which just gauges your ability to express yourself. If you can do that... well, it's pretty easy to do well in.
I did, however, use class time very, very productively. I just don't study at home, even now at uni

I need to force myself to go to a library before I'll even open a book.