You 'waive' your rights to a certain degree. Then federal law steps in to prevent discriimination based on sex, race, age, creed, religion, or beliefs.
If a student who is known to be emo or scene (sorry for the emos out there but they actually make a great example for my case) my dress in all black clothing, listen to sad depressing music, and may appear to take part in self - harm. The school pulls them aside and asks them to subject to a random search of his backpack. They find the following: some notebooks of stick figures hanging from trees, an iPod, some CDs of Dashboard Confessional, a couple of textbooks, a condom, and what appears to be grass wrapped in a baggie. The student is corralled into the office, his parents are notified and the student is expelled from school on the suspicion of having possession of the drug known as weed. The kid goes home, texts some of his friends and finds out that 5 others in his group were also pulled aside, searched and expelled under suspicion.
The parents fight the school and ask to have the substance appearing as grass in a baggie tested.
The school says they have already disposed of it. The student says it was not really weed, but was instead part of a school project involving weed. He had taken some lawn clippings and put them in a baggie and was going to use it on an anti-drug poster. His teacher confirms the project. The school is then sued for damages, must repeal the expulsion, and completely reinstate the student with no penalties, and the district is forced to repay the parents their lost wages for missing work and must repay the students for damages incurred to their records as well as reputations, as one student was fired from his part-time job when word of his expulsion reached his boss.
All six students who were expelled that day went on to graduate with honors from other districts, 5 of the 6 went on to college, two dropped out of college their freshmen year, 1 transferred to a community college to pursue an associates degree, and one ended graduating from college magna cum laude. The other went on to pursue a masters of school administration.
Same school district different crowd - a cheerleader with a known drug addiction among her friends - often shows up for class high, cheers while high, and is from a rich upscale family. But because she puts on a nice front that she maintains a good GPA, is involved in cheerleading, and sometimes attends church, no one ever thinks to stop her although all her friends know she's got the goods with her most of the time.
This cheerleader gets a scholarship to a 4 year university, however by Christmas she has allowed her addiction to heroin to take over to the point that she has lost her scholarship because her grades have fallen. Due to the loss of her scholarship she is no longer allowed to participate with the university cheer squad. She becomes depressed, uses even more until she is caught on campus with drugs, is expelled from university. She moves back home, hides her drug problem from her parents saying she was just overwhelmed and just decided to drop out and take a break for a year.
She continues to use, her parents continue to support her habits without realizing it saying she needed the money for something else. A year later she is selling herself through prostitution to pursue her ongoing addiction. Whatever money she makes goes to drugs. Her body is ravaged from the drugs, malnutrition, (she too busy either having sex, getting high, or looking for her next fix to even think about food). One night she overdoses, is rushed to the ER where she enters cardiac arrest and never recovers. She dies in ICU overnight. The headlines in the local paper then reads: FORMER CHEER ALL-STAR AND LOCAL BEAUTY QUEEN DIES IN HEROIN OVERDOSE.
Two different people - one group is targeted just for their looks, the other completely overlooked and by-passed simply because 'they were too good of a kid to be suspected of such behavior'. It sounds really radical and extreme but it does happen. Many high-school stars have fallen victim to drug addiction and were completely by-passed while the punks were singled out when the reality was that he was the cleanest kid.
The above was a hypothetical situation, but it can and does happen.