Conservatives want as much freedom as possible with voluntary restraint so that some governing authority doesn’t control our behavior for us.
You don't understand libertarian philosophy at all (big or small L). Libertarians want people to determine ethics and morality based on their own faith, education, and family values. They don't believe that "some governing authority" has the inherent right to control our behavior except when it impinges upon another person's rights. This belief is consistent with that of the Founders. For those of us who believe in God, the source of our code of ethics is our faith. It certainly isn't some bureaucrat in Washington.
In this particular instance, libertarian philosophy strongly supports the right of free choice in association, and the right of individuals, businesses, and organizations to set the conditions under which they engage in transactions. There is no basis whatsoever under libertarian philosophy for the girl to argue about the rejection of her picture - it doesn't meet the requirements set by the yearbook committee, and they are therefore fully within their rights to reject it. Of course if she wants to publish her own competing yearbook with whatever kind of pictures she wants to put in it she is welcome to do so.
The existence of a compulsory government school is what leads to the legal challenge that the student may make. If she didn't attend a government school she would have no basis whatsoever to bring any legal claim about the yearbook policies.
It’s always amusing when someone disagree with you to hear them say, “You don’t understand blah blah at all.”
I do understand libertarianism.
And I understand, perhaps better than you do, that it is closer to liberalism and leftism than it is to what our Founding Fathers implemented...a system that allowed the most freedoms in a framework where the morality was maintained by Judeo-Christian religion and anarchy and license were held in check by a populace that willing controlled their behavior so that others wouldn’t demand a strong government to do so.