I went to school for 6 months in Japan at a school with a very good reputation (YAMASA). I found it very disappointing.
The problem is IMO that the way they learn to teach Japanese at university is very poor. Japanese teaching as far as I can tell is far behind English teaching, which is already crappy. Here is a typical day in my schooling.
1. Teacher enters classroom, chats with class for 1 minute.
2. The weeks vocab is reviewed through (kanji showed and we read, pitch is typically over pronounced by the teacher).
3. A new grammar point is presented usually without any context. This means this.
4. A handout is given to all the students with sentences with blanks in them. We fill in the blanks with the grammar, making sure to use the correct form.
5. At the end the teacher asks some students to read out each one (ie Tom please read your answer for 1, Sarah please read your answer for 2.. Usually it will just go around the room)
6. Students then do the next section, there will be sentences with blanks, but this time the grammar is already there, you need to choose a word appropriate to the sentence for example 高かった!以外にも____ (It was expensive! However, to my surprise, _____).
7. Again once finished students are prompted to read out their answer for each one.
8. Same again, but this time the blanks will be the other side of the grammar eg _____、以外にもおいしくなかったです。(______、However, to my surprise it wasn't delicious)
9. Feedback again.
10. Do some dialog with humor aimed at 12 year olds probably involving someone having a crush on someone. You practice in pairs.
11. Now comes the fun part of the lesson, there will be a dialog where you can change the blanks each time you do it. This is done with a partner. Often there isn't time to do this.
Homework is more sentences with blanks to be filled. Repeat a lesson like this 4 times each day. The teacher talking time is about 90% and then the students that are outgoing get about 2% each, the rest are lucky to get 1%.
I taught English for 2 years in Japan and have a CELTA teaching qualification. I have also read books on teaching. Not saying I am that great, but I know the theory pretty well. This school sucked and from what I can tell it is not unique. I tracked the improvement of my classmates over the 6 months and it was pretty minimal. I also studied a bit with the top class and their speaking was horrible. I actually wrote a 40,000 character report on the school and sent it to my teachers.
As you can probably tell I am a bit bitter. Most of the other students had no clue on the best way to learn languages or teaching, so they could enjoy it for what it was. I on the other hand was painfully aware of how bad they were. Studying on my own was many many times more valuable than that school.
So my advice is don't go to school. Even if you find a awesome school where lessons are really fun and involving, it won't be worth the money. Why don't you do homestay? It will be much cheaper and more valuable IMO.
Also, you should probably read everything on
http://alljapaneseallthetime.com/ about "fun" and "study". RTK1 should be about the extent of study you do, at least for long periods. Once you finish that you can choose to take a path that involves study (eg KO2001), but if you don't feel like doing it or get bored, stop but keep Japanese involved. Other than doing SRS reps and adding to my SRS I never study these days.