Here are a few facts that should matter to your parents:
1. Sorority women have consistently higher grade point averages than the unaffiliated students at the same college. Academic achievement is very important to sororities.
2. Sorority women have much higher graduation rates than unaffiliated students at the same school.
3. A sorority makes a large campus in a strange town (and country!) much smaller. In addition to giving you a social life, a sorority provides you with a support system right away which can help you adjust to being so far away from home (and should keep you happier an more motivated to stay in school and do well!)
This web site could provide your parents with some more insight on the benefits of sorority life from the perspective of the parents of sorority women:
http://www.sororityparents.com/