In short, this British study shows that, particularly in primary school, the more girls there are in the classroom, the more poorly boys do in English class...by one-tenth of a grade for a moderately higher percentage of girls. The reasoning is speculated to be that boys are discouraged to see girls doing so well.

I would point out that to say there are more girls is equivalent to saying there are fewer boys. If you're guessing the cause, then one framework is as good as the other. According to the statistics, girls are stone-heartedly unaffected by the number of boys in the classroom. (I added the stone-heartedly for dramatic effect.) But, the article points out, strangely, that girls do better if there are some boys in the class who receive free school meals. (I didn't make that up.)

Is there a literary consequence to this? No. None. Nada.

Oh, wait, maybe the boys are so depressed at seeing girls excel that they aggressively seek ownership and control of publishing companies and thereby suppress women's publishing opportunities.