Qualified language school wanted

[Caerula]

Hey, I did´nt know where to put my question so I opened a new thread - I hope, that´s ok.

I have an (for me) important favor to ask:
can somebody recommend me a good language school in Osaka or Tokyo? I also catched up on Fukuoka, but I´m not sure about it yet.
I prefer Osaka, though I couldn´t find any qualified school there in web.

I´m planning to go to Japan next summer for about a month to study the language more intensively. I´m currently studying Japanese at Japanese Culture Institut in Cologne - I really want to learn as much as possible in this month.
Maybe I should also mention that I would like to make a year abroad (in 2 or 3 years) for working at an German Primary School (teacher is my profession).

I hope you can help me All my thanks in advance!