Simplify the following text for a Grade 7 native English-speaking person.
Original: The team won its first race at the 2009 Australian Grand Prix , with Jenson Button winning six of their first seven races and ultimately going on to win the 2009 World Championship while team-mate Rubens Barrichello claimed victory in Valencia and Italy .
Simplified: Jenson Button won six of their first seven races of the season , and won the World Championship . His team-mate Rubens Barrichello won at Valencia and Italy .