Often it is good to challenge your higher level students to form and express an opinion. To do this you can start with the question, "What do you think about (something such a current event, state of affairs in Japan or the world or anything)". Then you demonstrate by showing them how you would answer such a question. You say "I think it is ….." or you teach them to say "I'm sorry but I don't have any opinion on that" or "I'm not interested in ……".
This kind of practice occasionally will really bring up the level of your students to use English for a real purpose. This builds confidence and gives you a chance to introduce new vocabulary, phrases and idioms that the student will be happy to learn. So give it a try!