The Post-Gazette's Mike White has an interesting piece on boys playing girls sports. It centers on the Greensburg Central Catholic girls field hockey team, which features five boys.
Boys playing girls sports is nothing new. The Washington girls volleyball team has a boys player and there have been the occasional occurrence in other sports. I can also think of a couple boys playing girls tennis over the years.
In most cases, I never felt the boy gave the girls team an added advantage. In the PG story, it's clear the GCC field hockey team has one.