Many of them cannot switch schools so they must endure the principal's new policies. Its as if they got a new boss at their company but they're not allowed to quit. Unfortunately, the protest degenerated into a riot. If the students had remained peaceful, most people would have have questioned the policies of the principal. Now the students, rather than the principal, are seen as the troublemakers.
Protests are an effective way to attract attention to a problem as long as they stay peaceful.
A peaceful protest will encourage people to reconsider the law that you are protesting. Many times an unjust law is written with any opposition because the politicians only focus on the law's positive impact. Not until a protest starts, do people consider the negative impact of the law. Keep the pubilc and the media focused on the law by remaining peaceful. And vote Libertarian so one day students in Miami will simply switch from one private school to another, rather than stage a protest.