My little neighborhood sandwich shop was invaded today by a horde of high school students from a school I'd never heard of. The students were more diverse than the neighborhood. If you're being as honest as Juan Williams, under such circumstances you might expect to see little signs of concern -- those side glances, women securing their handbags under the table -- that you see from older people when a group of teenagers suddenly appears. There was none of that. None. Part of the reason was that the teenagers happened to be well behaved. But the real reason, I think, was the sweatshirts and T-shirts they all wore proclaiming their attendance at Pacifica Christian High School.

Oh, yes, and collared shirts and tennis shirts and khaki shorts or skirts, with fashion accessories limited to the occasional scarf.

This is the uniform of the relatively new Christian high school around the corner, which has grown each year since it was founded just a few years ago. And it is big enough now to have enough seniors to be noticed at the sandwich shop.

A uniform says a lot. It communicates, immediately, that these are good kids, not gang kids, kids trying to get an education, not protect turf. The first thing Green Dot Public Schools (whose board I'm on) did when we took over Locke High School in the Los Angeles neighborhood of Watts was put the students in very similar uniforms.

I joked with my son that if a gang ever wants to take over Brentwood, they should show up wearing Pacifica Christian sweaters. They would be treated with great courtesy.

Most of us have uniforms. The good ones -- Hillary Clinton's black suit, when she finally found it, with the rotating colored shirts -- not only help you get dressed faster in the morning, but also convey to people who you are and what you want them to think of you.

A black suit says serious and smart; colored shirts say approachable and fun. Hillary.

Baggy shorts hanging low and the rest say gang member. The only thing crazier than gang members dressing like gang members is kids who aren't gang members trying to dress as if they are.

Bad uniforms -- and they are everywhere today, from fifth graders to young attorneys -- send signals that are utterly inappropriate to the person, place or time. For example, 11-year-old "designer queen" sex pots. (No, I am not suggesting any excuse for pedophilia; only that if you don't want your daughter to convey sexual signals, why dress her that way?)

I once asked one of the proverbial "other mothers" whose kid was far more stylishly dressed than I was (and I was doing better than usual that day) whether she agreed that how we dress our kids (or let them dress) is much more about values than about how much you can afford or the hottest styles. She found it a rather shocking notion.

The right uniform -- a blue sweatshirt from a Christian school that upon further inspection inculcates the very values that good stereotyping would associate with an urban Protestant school -- paves your way in the world, sending the right message about who you are.

The wrong one? In some parts, it can get you killed.

Examiner Columnist Susan Estrich is nationally syndicated by Creators Syndicate.