The other day, my teenage son had a choice. No, he can’t vote and no, he wasn’t ordering a sandwich at a diner with an 18-page menu. He was with some friends who decided they wanted to get a better view of the street and, presumably, their peers who were walking below during a warm fall day.

They headed for the roof of a building, where a Private Property No Trespassing sign awaited them. They ignored the sign. When my son hesitated, they signaled for him to join them.

“Oh, come on, you’re not going to be like Joey,” they said in a complaining tone. I don’t know who Joey is, but when I heard the story I instantly wanted my son to meet him and hang out with him.“No,” he replied, “but I’m not going up there.”

What stopped him? Why didn’t he do whatever he wanted to do or, equally importantly, whatever his friends wanted? The other boys clearly expected him to fall in line, just the way our friends, our parents’ friends and our grandparents’ friends expected us and our ancestors to fall in line, too.

We send our kids to school every day to learn about differential equations, the American Revolution, the powerful prose of Ernest Hemingway and the anatomy of frogs and people, but somewhere along the lines, they have to learn to develop a set of values.

That can come from a dedicated teacher, who takes time out from a demanding schedule to teach a broader life lesson about the difficulty of making the “right” choice. It can come from a coach, a principal, a neighbor, a parent, a grandparent or anyone who goes out of his or her way to make sure that our children don’t lose theirs.

I understand that this moment isn’t the biggest challenge my son will face. Undoubtedly, someone will come up with an idea, a suggestion or a dare he feels pressure to do.

These small moments, however, lead to the bigger ones. It is the slippery slope argument. If doing something that might be a little wrong doesn’t cause problems or have any consequence, maybe doing something larger that might not be exactly right is also just fine because no one noticed or he didn’t get caught. Or, the argument that frustrates me the most, someone else did something worse, so this isn’t such a poor decision.

We all have those difficult moments, when someone whose company we enjoy encourages us to do something that might not be in our best short- or long-term interests and when, for whatever reason, that friend insists we participate to demonstrate our friendship. This is the moment when peer pressure threatens to silence the little voice in our heads that says, “This is probably a bad idea.”

We hear so many times about people who either don’t have that little voice or who have so effectively silenced it that the rules of our country don’t apply. They live with a freedom that they find exhilarating, until they get caught.

We are painfully aware of the destruction people who tumbled down that slippery slope create for themselves and society, through difficult and self-destructive habits.

There are so many other children who, thanks to the effort of the village of supporters around them who point to a true north, develop both self-control and self-confidence that allow them to say, “I’m not going to do that.”

Through any age, one of the hardest words for us to say, when those around us encourage us to join them in treading on someone else’s property or rights, is “No!”