I know that my highschool would always send one of the 12th grade mechanchot yearly to Israel so they could check out each and every sem b4 just sending their students to some random seminary.
Also, at this point since they are doing many many years of this, they know the hanhala from the seminaries quite well and are able to understand what the seminaries are really about. I think this was a huge plus for many of us getting ready for seminary.