Leaving and entering without a Visa

I am an american and realize that you don't need to apply for a visa unless you are staying in Japan for more then 90 days.

I am going to be spending 6 months at a school in the Japan, but I don't nessecaraly have the 150 hour prerequisite of Japanese language experience required for the Pre-college Visa.

Should I apply for something like a working-holiday visa, or would I just be allowed to enter the country, go home for a few weeks just before the 90 days is up, then be allowed back into the country for the remainder of the class.

I was leaning towards the second option, but I am unsure if I'll be stopped re-entering the country on the second time and questioned along the lines of "what are you doing back so soon?"

I appreciate any advise

As an american you don't qualify for a working holiday visa.

I am unsure if I'll be stopped re-entering the country on the second time and questioned along the lines of "what are you doing back so soon?"

You always run this risk although I don't think it'd be too much of a problem if you only do it once.