> If so it’d turn around a long held belief that STEM education is biased towards men. At least in grade school.
No, you can't infer this conclusion from that paper.
Yes, the paper claims that there exists some bias towards girls (from teachers' grading). And the sentence you quote claims that without that specific bias, the gender gap would be in favor of boys ("12.5% larger"). However, we do not know if this figure is free of bias (IMO, fair to say probably not). Therefore, there might be other biases in STEM in favor of boys that could explain the gender gap in their favor.
It's unlikely. You're suggesting there's an even bigger bias but one which we've been unable to quantify scientifically to even a limited extent (compared to this study, which provides clear evidence)
No, you can't infer this conclusion from that paper.
Yes, the paper claims that there exists some bias towards girls (from teachers' grading). And the sentence you quote claims that without that specific bias, the gender gap would be in favor of boys ("12.5% larger"). However, we do not know if this figure is free of bias (IMO, fair to say probably not). Therefore, there might be other biases in STEM in favor of boys that could explain the gender gap in their favor.