No, students, especially those who are members of the National Honor Society, should be allowed to wear its regalia. Being an honor student should be an aspiration for students, and they should be proud to wear the regalia. Being able to show off your accomplishments is a motivation for some people.
Students need to be honored and rewarded for the hard work that they complete. Wearing their National Honor Society isn't to put other students down. Instead, the purpose of this is to honor them for the extra time and effort that they gave. In the real world, everyone's accomplishments are not equal.
I am in disagreement with the ruling that Plano Senior High has put into effect which does not allow its students to sport National Honor Society regalia at their graduation ceremony. Any student who has worked hard to earn something he is proud of should be able to openly display it.
If it is a good thing and they are representing their achievements then I do not see an issue here. If it is because other students might feel inferior that is complete idiocy, if anything it would motivate people. If you won an award you should be able to show that as long as you're not rubbing it in people's faces.