Complex sentence: The school was opened in August 2006 and originally taught only freshman and sophomore classes; by the first semester of its 2008-2009 school year, Valley Vista began teaching all four regular grades.
Split into simpler sentences: The school was opened in August 2006 and originally taught only Freshman and Sophomore classes. By the first semester of its 2008-2009 school year, Valley Vista began teaching all four regular grades.