accredited schools

Why is it that some schools/programs are accredited and others are not?

I graduated from an Art Instit. school and when I applied for grad. program at a Uniy they said the Art Instit. isn’t accredited by their regional standards. I went to the AI website were they are listed as an accredited independent institute and have some art accredidations by local groups.

Years of schooling and money out of my pocket and what am I left with, a piece of paper from a post secondary independently private institution with local state accredidation from private groups. If I want to go for a grad. program I am going to have to start all over again.

Any suggestions would help.