Only the 70s?
Still, I have asked myself the same question and wondered why others seemed not to ask it.
Anyone remember the feminist complaint about the supposed preferential treatment paid to the boys as an explanation why girls underachieved?
Penis envy run amok. Biologically males have larger brains than females. It's not fair! Leftism requires that females be given more education resources and males less to level the playing field.
It was the absense of Ritalin and the relative scarcity of special ed before the 80s. Now, being an active boy (or girl) causes teachers to refer kids for Ritalin and special ed classes starting in kindergarten.
Since the 70s and IDEA legislation, more money and thus more kids (usually boys) have been targeted with psychological services in schools and put in special ed classes, which ensure that they never achieve.
Those boys (and girls) who were usually more intelligent and more intolerant of pedagogical BS had to be dealt with in the regular classes. Now, they shuttle these kids off to the side and medicate them into compliant, brain-impaired kids.