College visa to pre-college visa

I am now currently residing in Japan on a college visa, as a graduate school student. I want to quit my studies in my current subject and university and prepare for entrance to another university so I want to enroll in a japanese language school from this april. I sent a mail to one of the language schools in tokyo and received an answer that'' I should continue my study in my current school and attend the language school in the time remaning from my studies, cause if I quit my school I won't have a college visa anymore and that it is hard to switch from college visa to pre-college visa.''
and no more explanation on the subject, what she said to me didn't actually make any sense to me. I don't understand why it should be harder for me to get a pre-college visa than other people who come to japan solely for language studying purpose applying for pre-college visas. Is there something I am missing? Is there any truth in what she told me?
and if I quit school and give up my college visa now how can I-that is if I can- receive a long term visa to stay in Japan till April?
Thank you in advance.

I heard from someone on this forum that Pre-college and College student visa status have been merged into one type by Immigration. So maybe it doesn't make any difference.