Yes, all rights have limits, I even said it in my post - and told you exactly what the relevant limits in this case are.

Sure, striking isn't ideal- but strikes and protest action is the only means those not-in-power have of asserting their rights against those in power when the latter oversteps their bounds.

There is absolutely no rational analysis that can conclude that hair-style rules are WITHIN  the bounds placed on authority in  the context of schooling.
Hair doesn't affect discipline. It doesn't intrude on other students ability to learn. It is not disruptive to class-room activities. 
There's no legitimate reason to HAVE rules about this, so having them is not a justifiable intrusion on student's rights.
Indeed I'm hardly unique in this consideration. Back in the early 2000's then education minister Kader Asmal ordered ALL government schools to scrap ALL hair rules - in this case for intruding on religious freedom rights.
His order was largely ignored.