High Schools in Japan?

My mother and I are moving to Japan in a few months. I would like to attend a university in Japan if it's possible, but my mother and I both agree that an extra year of high school might be best so I could get a feel of what school would be like in Japan. I don't want to use a program since I'll be moved down there anyway, so how would we go about doing this? Is there a certain procedure we must do?
Also, I'm graduating in 2 months... will this effect my chances of getting in for an extra year? I'm only 17, technically I'm supposed to be a Junior but I started school early.
IF ANYONE KNOWS PLEASE, PLEASE let me know.

Cortney, are you saying that you wish to enroll in an ordinary Japanese senior high school that have classes in Japanese language? If so, you much Japanese can you speak, read and write? Or are you willing to go to an international school? Also is there a specific area you are planning to live in? The answer to your original question differ depending on these matters.

I don't know much Japanese, and I don't want an international school (being put into a high school would force me to learn Japanese quickly... *others I have talked to who did go to Japanese high schools without any Japanese experience informed me of this)
I was thinking the Tokyo, Shibuya, or Kyoto area.

Why not talk to the "others" you mentioned who told you about going to a Japanese High school? They would know the best if they experienced it.

Well, to begin with, in Japan, senior high school (which consists of 3 years for people of ages 15 to 18) is not compulsory education. Therefore, in order to enroll to a senior high, you need to pass some kind of an examination which is designed to make sure you can keep up with your classes that are held in Japanese, to say the least.

Exchange students are excused from these exams, because they aren't expected to keep up in class anyway. They are here to learn bits and pieces of the culture, and their basic academic skills are to be completed in their home countries.

There are however exceptions. For example, a lot of returnees (Japanese children who spent time outside Japan due to parents' jobs) are allowed to take special exams that will allow them to enroll without high Japanese skills.

Cortney, you seem to have friends who experienced similar things. Perhaps you can ask which schools they went to and how. Otherwise, you or your mother can inquire at the Board of Education of the district you're planning to live in, or at the Japanese Embassy near you.

Good luck.

note that high schools in Japan are very unlike universities in Japan. They are completely two different things. So I'm not sure if "getting a feel" of what high schools in Japan are like will help your life in college.

How about going to a language school in Japan, and then to "yobiko" cram school to study for univ. entrance exams?