Complex sentence: Yuba City High School's athletic program used to loose in the athletic Metro League; however, with the opening of River Valley High School, Yuba City High School now looses in the Tri-County League.
Split into simpler sentences: Yuba City High School's athletic program used to be a member of the Metro League. However, with the opening of River Valley High School, Yuba City High School is now a member of the Tri-County League.