What are the greatest moments in our lives? How do we keep from ruining them?

I had these worried thoughts after Bill Laux told me why he was forced to watch his only child’s once-in-a-lifetime high school graduation on closed-circuit TV as he smoldered with resentment and regret.

He arrived before the ceremony began. There was plenty of room in the field house. But the Fairfax County police officers monitoring the West Potomac High School graduation at Hayfield Secondary School said he could not go in. It was the spillover TV auditorium or nothing.

It is hard for me to imagine an event with more emotional resonance than a high school graduation. And yet it carries such potential for disaster. Other big moments such as weddings and funerals usually draw smaller crowds. College graduations can be huge, but we expect that and aren’t grief-stricken if we don’t see much.

High school ceremonies, on the other hand, involve parents such as Laux with great hopes and deep connections to the school. We have attended the games. We have staffed the fundraising carnivals. We have met many teachers. Our more talkative kids give us regular reports on what is going on. It’s our school, too.

What happened at the West Potomac graduation will be difficult for Laux and other shunned parents to forget. Supervisors would do well to note in particular Laux’s account of one father who let his frustration go wild.

That father had the same experience as Laux. The invitation said the ceremony began at 3 p.m., but there was no warning on Laux’s ticket or anything else he received that no one would be admitted after that.

Traffic was a mess. There was no parking at the school when Laux arrived at 2:45 p.m. He dropped his wife at the front entrance, found a makeshift spot and hurried back with many other frantic parents. A kindly woman told them they would get in but needed to wait until the 500 graduates had lined up and entered.

Yet, once that happened and they approached the entrance with their official white tickets, the police said no. They had their orders, even though, as Laux’s wife later told him, there were plenty of empty seats, including the one she had saved next to her.

The overflow TV auditorium was noisy. School security officers were yelling at people to be quiet. After some preliminary awards, Laux went back to the field house to see whether the police were letting parents in at least to see the diplomas awarded.

They were not. The father Laux told me about finally cracked. Laux said he watched the man “engage a police officer in a heated, profane attempt to enter the field house. After he was denied, he walked 15 feet down the security tape, ducked under it, and made a dash for the entrance door. The police caught him, grabbed him around the shoulders and physically restrained him. After more yelling and profanities, they pushed him back toward the TV auditorium and gave him the choice: jail or watch on TV.” He slumped away.

Laux did, too. He watched the big screen as he remembered his many hours as a marching band dad. He had repaired instruments and equipment. He had traveled to competitions all over the state. He had been captain of the Pit Papas fathers group, which unloads band equipment on and off the marching field, for three years.

Assistant School Superintendent Scott Brabrand has since e-mailed Laux, saying he was sorry about what happened. School officials say they have reviewed the event carefully to prevent future mishaps. Next year, the school will use the more spacious Patriot Center.

That should have happened this year. High school unites more people in more ways than any other public institution. The memories are strong and lasting, for good or ill. Graduating from high school is, for many, the biggest of the big moments. It is also the most vulnerable to heartbreak if we don’t do it right.