You misconstrue abuse of power by the court as the court's true power and responsibility. We had a very activist court in the 60's and 70's, a court that many Americans reacted against and I know many people who only vote republican because of supreme court nominations. Activism can backfire, it can make the american people react against whatever political idea is being advocated, potentially leading to a reversal of the decision in the future. The court misconstruing the Constitution to serve their own political whims is a threat to the very foundation of this republic, a court refusing to enforce the law, regardless of implications, is both dangerous and, in the case of the supreme court, treasonous.
Fortunately, I have faith that a majority of our current justices are strict constructionists and will do their best to rule in accordance with the letter of the law, and not their own political, religious, ethical, moral, etc. posistions. There's a chance you may be right about the court being activist, as two of the members are yet unproven, but I certainly hope not.
And yes, we can say that checking a student's purse on mere suspicion in school is unconstitutional, it is simply that the court (or, more accurate the court in 1985) failed to uphold the constitution. This is something I dislike about systems of common law, bad and even illegal decisions tend to stand because of custom, while in a civil law system a bad decision would simply be ignored when the next issue came up. Ultimately the flaw is in human beings, the perfect judge would be a computer capable of understanding all the issues all the history and all the law, but rule without emotion, political agenda, ethics, or morals...rule only according to the law. This is what we call upon our Justices to do and while some do a better job than others, none are perfect.