Sophie prefaces our departure for her final field trip of third grade with an increasingly common request: “Dad, please don’t embarrass me.”

I assure her that is never the goal, only an unintended, and probable, outcome.

This last school outing is ambitious: Some 75 third-graders, plus teachers and a smattering of parent chaperones, will board three school buses for a 2 1/2 hour ride to Grand Isle. Once there, the kids will, in theory, learn about Louisiana’s coastal erosion at the front lines.

Sophie’s concerns about potential embarrassment notwithstanding, she insists on sitting next to her dad for the epic journey. We claim the last bench, the traditional province of cool kids.

And, unfortunately, the bumpiest seat on the bus. Cars are far more user-friendly than 40 years ago. The classic yellow school bus, however, has remained essentially unchanged. Neither the technology nor the comfort level have advanced much since I was a kid.

Traveling on New Orleans and south Louisiana roads in a school bus is not unlike riding in a submarine being dragged by a tractor. We bounce like popcorn.

For at least one of Sophie’s classmates, this road trip represents the longest journey of her life. After two hours in the bus, it starts to feel like the longest of mine.

Mile after mile along Louisiana Highway 1, we traverse the economy of south Louisiana, with its bayous and barges, shrimp boats and sugar cane, offshore rigs and fishing rodeos.

Eventually, Highway 1 is reduced to a thin ribbon of asphalt surrounded on both sides by open water. The city kids are oblivious, chattering away in their self-contained world.

Informed that Grand Isle is, in fact, an actual island, Sophie expects something along the lines of “Gilligan’s Island.” “Mary Ann is my favorite,” she says. Her dad’s, too.

Alas, there are no marooned movie stars or bumbling millionaires to greet us on Grand Isle. Only a procession of raised camps with cute names (“Weathering Heights,” “Reel Life”).

At Grand Isle State Park, we finally disembark and ascend en masse to the park bathrooms in a raised Acadian-style cabin. That long-overdue mission accomplished, we are divided into four groups to take turns at different, 30-minute activity stations.

Our group, happily, is second in line for lunch. The “cafeteria” consists of the cement pad under the bathrooms. Galatoire’s, it is not. The kids notice the pipes high above our heads coming out of the bathroom floor.

As part of my chaperoning duties, I explain that these pipes connect to the sinks and toilets. A collective “ewwwwwww” erupts.

During lunch, Sophie apologizes to several classmates for what she believed to be her team’s excessive bragging after an earlier, ecology-themed competition. Discussions veer from Harry Potter to favorite dinosaurs. Sophie cites the “Sam-o-saurus,” named for her 6-year-old brother: “They’re very destructive, and they like ice cream.”

After lunch, we are to plant grass on the beach. En route, girls hold hands and boys kick rocks at each other, which pretty much sums up third grade.

The beach reeks. The previous afternoon, a fishing boat’s net burst just offshore. Thousands of dead menhaden, known around these parts as pogies, washed ashore to rot.

Bulldozers are at work, cleaning up the fish mess but not the fish smell. Two big trucks are parked on the beach grass planted the previous week by another school group.

One step forward …

Undeterred, Sophie and her classmates gather around Dr. Pam Blanchard, the Louisiana State University professor who co-founded the LSU Coastal Roots Program. Coastal Roots encourages schoolkids to become stewards of the environment by growing and planting beach grass to counter coastal erosion.

Blanchard selects two student volunteers, identifying one as “Mr. James.” That cues his buddies to take up a mocking chorus of, “Mr. James, whooo-ooo!”

The professor isn’t having it: “Don’t make fun of people,” she scolds.

Moving on, she refers to the nearby dunes.

“Why are they called ‘dudes’”? one boy asks.

Today’s task is to plant a type of beach grass called bitter panicum. “They are very sturdy plants,” Blanchard notes.

They better be, to survive bulldozers and third-graders.

She continues, “These are the coolest plants.”

A boy challenges her opinion: “What about a Venus flytrap?”

“That’s also very cool,” Blanchard concedes. But not particularly useful for combating erosion.

Armed with shovels and plastic tubes containing plugs of bitter panicum, the kids get to work. They dig diligently, only occasionally stepping on the newly planted flora.

Following a beachside seminar on Louisiana’s disappearing coastline, Sophie is glum: “That ruined my summer. Now all I’ll be thinking about is erosion.”

Which prompts another girl to wonder out loud, “What’s erosion?”

The day’s lesson may not have taken root as firmly as the bitter panicum.

All too soon, it’s time to board the buses for the long ride home. Some riders contort themselves on the hard seats for a nap. Girls braid each other’s hair.

A boy flips his baseball cap — actually, his father’s baseball cap — backwards. It bounces off a certain chaperone’s shoulder and flies out the window, rolling along the highway like so much tumbleweed.

The hat trick, not erosion, dominates the back-of-the-bus discussion for miles.

We arrive at school far more sweaty, dirty and tired than when we departed. And maybe, just a bit more aware.

Staff writer Keith Spera chronicles his parenting adventures in the occasional ‘Parental Advisory’ column. Follow him on Twitter, @KeithSpera.