Is it possible teaching English Subject by using 100% English language as working/intermediate language?????

I think teaching English using 100 % English language can be applied, but with some consideration, such as: class condition/class type.
If we teach English in International school, teaching by using 100% English Subject is absolutely. Since we know their competency in learning English. Talking about this issue, I got a suggestion to learn about CALLAN METHOD. Here at glance I know that, It is can be assumed as new style in teaching English. There are actually many sites on the web that pertain to the Callan Method of teaching English. There are some PDF files that will help us and some schools in London that can also lend us assistance.
Source(s):
http://www.callan.co.th/Html/callanmetho…
http://www.englishforums.com/English/The…
http://www.englishforums.com/English/The…
http://www.callan.co.uk/callanschool_stu…
http://en.wikipedia.org/wiki/Callan_meth…
http://www.callan.co.uk/
On the other hand, if we teach English in ordinary school/conventional school whose ordinary students' English competency, I think teaching by using 100% English language is not the best choice. Since we realize that teaching English can not be separated with the contribution of culture in every country. Each country has their own certain vocabulary, so if we teach without sometimes translate it into the native speaker' language, I think it's impossible. Even for RSBI program in Indonesia, in the real implementation of real standard of international, in teaching English and other subject, some teacher are still have had teaching use their Indonesian language during class activities. I think and believe that mother tongue and first language still become part of the teacher habitually, even they speak proficiently in English and great in teaching.