Recently, my 12-year-old son and I entered the subway station at 96th Street and Broadway. On our way to the downtown platform, we saw a young teen boy being frisked and questioned by police. The young man was either light-skinned black or Latino, and he was dressed in the style fashionable for kids his age -- low-waisted skinny jeans, belted across his hips, a t-shirt, and a fitted baseball cap sitting atop his curly Afro.

As we walked past, my son leaned into me and said in a half-whisper, "I wonder what that kid did."

Sometimes, we mothers manufacture teachable moments. We take them to see films like "42" as a way to talk about integration and ongoing racism in professional sports. We make sure they're aware of cases in the news, like the Trayvon Martin case, to teach them lessons about law enforcement and criminal justice (and injustice).

And sometimes, you happen upon the teachable moment in the course of going about your daily business.

I told my son, "You know, it's possible that kid did do something. And it's possible he did nothing at all."

I explained that he was seeing the NYPD's stop and frisk policy in action, under which police had the right to stop, question and frisk people for any reason and for no real reason at all, whether they were doing "something," or not.

"One of the problems with stop and frisk is exactly how you reacted when you saw that kid," I said. "Your first thought was, 'I wonder what that kid did. He must have done something bad.' He may have been perfectly innocent, but the first thing you think when you see the police pushing someone around is, 'that person must be a bad person.'

This is how stereotypes get reinforced. If the only people you see being pushed around by the police, and arrested on TV, are people of color, in your mind, you can't help but think, 'those people must be bad people.' This happens, regardless of the race of the person absorbing these images.

I concluded by reminding my son that, as a black boy, he was likely one day  to be in the same position as the young man we passed -- and that he would hate it if people assumed he was guilty of a crime simply because he was being harassed by the police.

My son felt badly for his initial reaction. I assured him that making him feel guilty for his reaction wasn't the point of my lecture. But I'm sure he kept it in mind when we saw the film "Fruitvale Station," about the murder of Oscar Grant. I made a point of letting him know a federal judge found the NYPD's implementation of stop and frisk unconstitutional - but reminded him the fight was far from over.

The enduring significance of the March on Washington is that kids can make a difference in the world. The film "The Butler" reminded my children that many of the foot soldiers in the Civil Rights Movement weren't parents like me, but teenagers like them who had a vision for a better world, and were willing to lay down their lives to see that vision realized.

After George Zimmerman was acquitted of criminal charges in the murder of Trayvon Martin, I made sure to tell my kids about the efforts of the Dream Defenders -- the group of young people who sat in at the state capitol building in Florida in protest of "Stand Your Ground" laws until the Florida legislature agreed to hold a hearing on the law. I told them about the many young people who helped challenge stop and frisk by taking cell phone video of their encounters, which helped dramatize how violative those encounters were -- just as cell phone video of Oscar Grant's shooting was probably the only reason Johannes Meserle was convicted and served any time at all for the crime.

My daughter is two years away from being old enough to cast her first ballot in an election. I remind her of the importance of the right to vote and how important it is to challenge efforts to disenfranchise young voters like herself. I want them to know there is plenty they can do, even now, to fight injustice as they see it.

That our youth have the power to change the world -- and deserve our support -- is one of many messages I hope is part of the celebration of the 50th Anniversary of the March on Washington.