
Girls face gender bias much more frequently in schools (and everywhere) than boys do. If gender bias caused hatred for the other gender then you’d expect to see women committing drastically more violent crime against men, especially historically, but in reality you see the exact opposite. Violence stems from entitlement, which boys inherit from patriarchy
Here are a few examples that come to mind with sources: 1) when women take up an equal share of time speaking in conversations (meaning men speak 50% of the time and women speak 50% of the time) women are perceived as speaking much more. Likewise, when women only spoke about 30% of the time, listeners perceived men and women as spending an equal amount of time speaking Source: Speaker sex and perceived apportionment of talk, Cutler & Scott
There’s another study that’s worth reading regarding the types of corrections teachers make when students are incorrect, and it found that when boys gave incorrect answers, they were much more likely to receive remediating responses, which involves telling the student how their answer could be improved or guiding them towards the correct answer. These are things like “think about this part; what if you tried X; why do you think that; you’re close, but…,” etc. Conversely…
Conversely, girls were much more likely to receive firm a firm “no” without further prompting; they were much less likely to be prompted to think about an answer so that they could get it right. The study itself was called Teacher Reactions to Classroom Response of Male and Female Students, by David and Myra Sadker, but it’s been in a few books too
There are other trends that have been shown across many studies, like boys receiving for attention from teachers, girls facing harsher penalties for challenging norms/expectations, girls having to work harder to be perceived as equally as capable, etc. You can look any of these up and find scientific support. Then you have history; women have obviously been excluded from the sciences, sports, positions of authority, and large sectors of public life for most of recorded history.
These longstanding biases don’t just go away when women get the right to have credit cards; we still face the effects of the “male as the default, women as other” conception that permeates even modern society. I recommend you read Invisible Women by Caroline Criado-Perez to learn more about these issues, it’s modern and scientific while still being digestible to the average reader
Most teachers are women in grade school. Women receive higher grades in school despite having lower avg SAT scores showing potential and likely bias in subjective grading. Women have made up any where from 50 percent to becoming the majority of college graduates for longer than you have lived. They are also the majority of graduates from most graduate education.