Earlier quoted context omitted.
A possible explanation is that most teachers in primary school are female, which creates an environment and behavioral expectations that favor girls, e.g.: - Teachers and the Gender Gaps in Student Achievement - https://jhr.uwpress.org/content/XLII/3/528 - Gender differences in teachers’ perceptions of students’ temperament, educational competence, and teachability - https://doi.org/10.1111/j.2044-8279.2010.02017.x
That seems weird though, right? Cause in the US teachers, especially for early-childhood, have been predominantly female since before this gap.
It could be that there were other external factors that used to counter-balance this effect, and are now being removed, such as, for example, the quest for increasing female participation in STEM no matter what, or general societal norms beyond school spurred by the rise of femminism.
In any case, the academinc literature on this topic is vast (and not so clear cut), so if you really have not seen thorough investigations on the topic beyond "boys don't like it" or something from the Bible you can start by reading papers citing those I mentioned above:
- https://scholar.google.com/scholar?cites=3048749496880924830...
- https://scholar.google.com/scholar?cites=8365905588440304050...