Should there be a dress code in places such as school, restaurants, places of business, etc.? Why or why not?

I believe that there should be dress codes in public places. It would not be appropriate to show up to an upscale restaurant with no shirt on an flip-flops. I agree with the idea of "No shoes, No service" i think even if your running in somewhere just to grab something you should have the decency to put some shoes on, plus thats just really gross if you don't!
On the other hand i think that sometime the dress codes in schools are a little extreme. I know that at my high school in Deer Park the dress code was extremely strict, but the regulations seemed to be different for each individual. I started to realized that the overweight individuals did not get told to go change if they were wearing something not school appropriate. I don't know if this was just coincidence but i think that if you are going to have strict dress codes they should stay the same for each individual.