On Monday, James and I went to the Muny in Forest Park. We were operating under the assumption that "Miss Saigon" was opening that night.

We parked about a bajillion miles from the Muny. On the walk to the theater, it was clear something wasn't right. "There sure are a lot of kids here for 'Miss Saigon,'" James remarked. I agreed.

A bit closer, we saw vendors selling T-shirts and souvenirs. Odd. And a few steps closer we heard children singing karaoke.

"We're all in this together! / Once we know / That we are / We're all stars / And we see that ..."

My finger is on the pulse of pop culture just enough to know that those are lyrics from "High School Musical," which was onstage at the Muny the previous week. We thought it had closed on Sunday -- the usual end to a Muny production.

It had not. The show was so popular that it was playing three extra days.

We decided to bite the bullet and stay for the train wreck that surely would ensue.

Neither of us had other plans. And I had read an awful review of the show in the Riverfront Times -- which I would link to if I could locate it on their terrible Web site (something to the effect of "How bad does a show at the Muny have to be not to receive a standing ovation? You have until Wednesday to find out.")

I had to see if it was as ridiculous as I imagined it would be.

On our way into the theater, we ran into P-D theater critic Judy Newmark. I asked her for her professional opinion, which proved accurate: It's a good story with lessons about acceptance and being yourself and whatnot. And it's best enjoyed by 6-year-olds.

My assessment: "High School Musical" was the worst thing ever performed onstage before a live audience. Ever. It was an OK made-for-TV movie -- yeah, I watched it once while channel surfing -- but it did absolutely nothing to hold my attention for two hours in the muggy nighttime air.

The family of possums that strolled across the batten (the frame atop the stage that supports the lights) definitely stole the show. Thank God somebody did.

Even worse than the show onstage, though, was the performance of the audience.

A few weeks ago, in this very blog, I classified "hell" as a trip to discount-grocer Aldi. I would like to revise that statement.

Hell is an 11,000-seat outdoor theater packed to the gills with ill-behaved children and their equally rude parents.

You would have thought we were in the stands at Busch Stadium.

People arrived late. And stood around in the aisles. And hoisted their kids into the air. And went to the restrooms. And talked. And sang along with the actors.

Overpriced beer made the experience only marginally bearable.

I realize that a show like "HSM" attracts a decidedly different audience from, say, "The Producers" the week before.

But it's really never too early to teach your loudmouth kids -- or yourself -- about theater etiquette for the times when civilized adults are seated behind you trying to get their $17 worth.

So here, free of charge, is a helpful reminder of unacceptable theater behavior:

• Talking
• Singing
• Arriving late
• Bringing in Taco Bell food
• Standing in the aisle
• Leaving your seat during the performance
• Photography
• Talking on the phone
• Leaving your seat before the actors exit the stage

To put to use a lyric from the show: "Getcha head in the game."

And leave the kids at home when "Miss Saigon" begins.