Passing the CHSPE is the legal equivalent of a high school diploma and therefore allows teen actors to work as adults.  This means fewer restrictions for production companies, allowing them to keep young actors on set for more hours and without the need for onset tutors.  Simply put, if casting comes down to a decision between two teen actors with similar talent and similar credits, the decision might come down to which actor can work as a legal adult.  In this situation, holding a certificate of proficiency might give your teen actor the edge to win the role.