Complex sentence: Freeport was formerly home to Freeport Elementary School on High Street, which all Borough students attended kindergarten through 6th grade, until 2005 when the school district decided to change the school into the district's Kindergarten Center, where all of the district's students attend kindergarten.
Split into simpler sentences: Freeport was formerly home to Freeport Elementary School on High Street, where all Borough students attended kindergarten through 6th grade. In 2005, the school district decided to convert the school into the district's Kindergarten Center, where all of the district's students attend kindergarten.