We have a exchange student from Spain attending this year with Aspect but she would like to return for a second year and graduate from our school. We now find out that we must become a SEVIS approved school. The home family is willing to pay all costs, but I am wondering how long this approval process may take--usually takes?

This may help,

Schools | Study in the States

It appears this process can take several months or more depending on how the requirements are met.

I would call the contact numbers for clarification.

http://studyinthestates.dhs.gov/contact-us