> Teenage boys everywhere have a widespread bias against putting in the effort to get good grades.

"Everywhere" as in "across the world and across time", "because testosterone/teen boys will be boys"?

If so, then I can give you an emphatic no, this is not at all true. It is, as with 99% of things, a cultural phenomenon. The degree to which the "bias against putting in the effort to get good grades" exists varies enormously depending on subculture and time. You may have personally only experienced cultures where this is the dominant case, but that does not make it indicative of immutable nature.

If not, then where and when is your "everywhere"?