Should I write "focus" or "focuses" in the following sentence?

The topic of telepathy is not very suitable for a science class, which focus(es) should consist of empirical knowledge and established facts.

I'm not sure if I should write focus because I'm talking about a class, or write focuses because I'm talking about empirical knowledge and established facts.

The topic of telepathy is not very suitable for a science class whose focus ought to be on empirical knowledge and established facts.

sounds (to me) better..