Complex sentence: In 2009 Balmoral Junior Secondary School closed and the building on Mahon became the second campus to Carson Graham, to hold the grade 8,9 and 10 classes while Carson Graham undergoes a facilities upgrade.
Split into simpler sentences: In 2009 Balmoral Junior Secondary School closed; the building on Mahon became the second campus to Carson Graham. It held the grade 8,9, and 10 classes while Carson Graham underwent a facilities upgrade.