My boys cannot successfully really partner up in this drill due to strength and size differences but I have used them in female gymnast group conditioning.

http://stjohn.org/HealthInfoLib/swArticle.aspx?1,2810

However, this article addresses a few more reason why girls are at higher risk for ACL tears.

To achieve that, start in the curled position, and the partner peels back the contracted muscle (i.e., true negative).

For girls, this exercise is incredibly important. As they hit puberty, the increased hip size rotates muscles in their legs away from knee support, and their hamstrings pick up a good portion of the load. When hamstrings are not stengthened, we tend to get more ACL strain, which lead to tearing.

There was a medical website that explained it really really well, but I couldnt find it.

Instead, a basic understanding can be found in section 1 of this webstite:
http://www.precisionnutrition.com/quad-hamstring-ratio

To summarize, if you don’t want to read it, excess load on the quad, with a weak hamstring, causes ACL tears due to the hamstrings inability to handle to stress from sudden turns or change in direction.