He's not stupid. Even when whackadoodle movements were far more open and popular, he was careful to only obliquely agree with those who insisted fluoridation was a government plot against the public, but that was enough to indicate he was opposed. And when he stated his belief that sexual repression caused cancer he hedged it enough that he could back off if needed, even as delivered the message. And so on.
My point is that Sanders has spoken against compulsory education in his middle-aged, openly radical days and TODAY he speaks of public education only.
Also that we know that Sanders still holds many political views from those days, just far more cautiously and usually deceptively expressed or carefully not talked about at all. Public schools and paved roads are socialism. Uhuh.
As for education, any state or community could maintain public education while eliminating the laws requiring attendance. Anti-tax, anti-education, and religious right Republicans in many states are trying to do just that.
Sanders is running for president and needs to affirm his commitment to universal compulsory education, thus disavowing his earlier feelings against compulsory education (and the harm it does to children would be desirable also). I searched before posting above and found nothing to indicate he has. It would take inclusion of one, but one critically important, word he once had strong feelings about.
To repeat, even in these dangerous times when increasingly fascistic conservatives are gravely threatening compulsory and funding for universal, education, and even though Sanders has spoken many times on education while running for president on the Democratic ticket, I didn't find that Sanders has stated his support for compulsory education.