Science magazine recently wrote a great article on research published in France related to gender hiring biases in academia in underrepresented fields such as STEM.
There are various studies done which highlight the gender bias hiring issues both ways. On one side of the coin, there is an argument that females get negatively discriminated in male dominated fields, while the other side of the coin says the exact opposite argument: females get positively discriminated in such fields because of under representation. The details on the study can be accessed here.
Thomas Breda and Mélina Hillion of the Paris School of Economics have done a comprehensive analysis of aspiring middle school and high school teachers who take written and oral exams. They have inferred that in male dominated fields such as STEM, the placements favor females by as much as 10% over males and the opposite is true for female dominated fields for male. However, they only favor them by 2-6% more.
Regardless of the applicability of this French study universally (experts have weighed in on its applicability and methods), it is always encouraging if female participation in teaching positions is getting better, for they would act as good mentors and role models for aspiring young girls who want to pursue STEM fields.