Is translating a good way to learn a language?

I'm an ESL teacher in Korea and my students' writing is absymal. They keep translating from Korean to English, even though I specifically told them it's bad to translate directly and they need to think in English. But since they're all doing it, I figured the least I could do is guide them in their translation. So I planned to give them a Korean text, have them translate that into English (and get their translations checked by me), and then write another similar topic in English. By doing that, I hope they'll learn the correct English expressions instead of expressions directly translated from Korean. Is this a good idea?