How long is a preparatory course for an international student?

I'm studying in Singapore. So what i am doing now is that after i got my 'O' level results, i went into a Community College. After earning my credits, then i will transfer. For me this is faster as the credits earned are transferable and when i go there, i do not have to repeat the courses and I am admitted as a transfer student. Maybe your student can go by that way also.