Schools absolutely do not welcome healthy masculinity in boys. Instead boys are being forced to obey, sit still for hours, study things they don’t want to and they are given punishment or drugs or social shaming if they behave in a masculine way.
The way school treats boys is absolutely crippling to a lot of boys, and distills in them a deep lived experience that masculinity is not welcome. This implicit message that their masculinity is not welcome, is given to boys in school over and over and over again, for years, during their most formative and impressionable time alive.
This is not some kind of wrong conclusion either that boys are drawing. Boys’s masculinity literally is not welcome in school. One essential part of masculinity is that most boys want to move and do things and explore and have freedom and follow their interests and passions. Boys are not at all allowed to be masculine in school.