I think that English classes in which used only English can help students to improve their language skill. I have two opinions to support this idea.

First of all, one of the reason that Japanese students are not very good at English is that they seldom have opportunities of speaking or listening to English in Japan. They need to have more chances and ones should be given students as much as possible to improve their skill.

Secondly, students in many countries with the exception of Japan have had English classes only in English for years. They are required to submit reports which are written only in English. As a result, most of them can use English very well. I think this way should be useful for Japanese students.

Because of these opinions, I think English classes only in English will improve Japanese student's English ability.