Different generations of the border wall with Mexico are seen from the United States in Nogales, Ariz., September 13, 2018. (Adrees Latif/REUTERS)

Laredo Community College solved its illegal-immigration problem with an eight-foot-tall, mile-long fence.

One day last August, I was on a ride-along with the Border Patrol when we received a signal from one of Uncle Sam’s motion detectors: Illegal aliens were advancing towards the Rio Grande. We arrived at the scene within minutes. Unfortunately, they were already gone.

From their tracks, it looked like three to four people. Not too far from where we stood, there were several roads and houses adjacent to the river’s edge. The aliens had likely either been picked up by a waiting vehicle or disappeared into a nearby house.

More likely than not, they are probably still in the U.S.

My days with the Border Patrol were arranged by the U.S. Attorney’s Office to which I had been assigned, and they served as an opportunity for me, as a new prosecutor, to get more familiar with the procedures, operations, duties, and responsibilities of the agency. The more I understood their job, the better I could do my job as a prosecutor.

Every day on the border felt like Groundhog’s Day, a never-ending cycle as 200 to 600 people illegally crossed every 24 hours in our sector alone. As they exited the Rio Grande, they cut through backyards, playgrounds, shopping centers, ranches, bus stops, and more. We would see them in our cameras and track them with our motion detectors, but we lacked the manpower to do much else.

Our sector has 200 miles of border. The Border Patrol simply couldn’t get everywhere in time. More often than not, they were too late. Our best estimate is that fewer than one in three illegal aliens were caught.

Not that it always mattered: Even after getting caught, some of the illegal immigrants would taunt us that they’d “see you again real soon.” (And sometimes, they were right.) From top to bottom, it was a complete and utter security failure.

But there was one spot on the border that was secured. A place where the people are safe. It’s the lone wall (well, technically it’s a fence) of Laredo.

Laredo Community College looks like any other university campus in America. What makes it unique, however, is that it’s directly adjacent to the Mexican/American border. Its southern edge runs a full mile along a calm and easily navigable stretch of the Rio Grande.

But despite bordering Mexico for a mile — in a sector with overwhelming numbers of illegal migrants, no less — Laredo Community College isn’t visited by illegal aliens. They avoid it entirely. The reason for this is simple: Laredo Community College built an eight-foot-tall security fence on its southern edge, just 150 yards from the Rio Grande.

Prior to this, the college had been having the same issues as everyone else. College administrators were inundated with phone calls about illegal aliens cutting across its campus. Though most aliens were nonviolent and left the students alone, not all of them did. There were thefts, assaults, robberies, and more.

Border Patrol agents were constantly receiving emergency calls about the mayhem on the campus — and of course, when agents showed up, the aliens would take flight, creating dangerous and disruptive chases. Can you imagine if your school or workplace were the site of quasi-daily law-enforcement hot pursuits? That was simply part of the Laredo Community College experience.

And although illegal immigrants were a nuisance, the real danger to the university and its students were the cartel members using the campus, specifically the tennis courts and parking lot, to make major drug deals. Right across the border from Laredo is the Mexican city of Nuevo Laredo. Like many border towns in Mexico, it has been completely taken over by the drug cartels. With alarming frequency I would hear gunfire from Mexico as the cartels fought one another (or, occasionally, the Mexican government). These cartels used to trespass onto the college campus to make drug deals.

At least until they built the wall.

It’s nothing fancy. It is made of wrought-iron bars and runs a mile in length on the southern side of the campus, right where the illegal aliens and smugglers used to cross to enter campus.

As it was being constructed, just like now, there was a lot of criticism and naysaying. You heard the same things you are hearing today: “They’ll simply go around it!” or “They’ll just go over it or tunnel under it!” and, of course, the insipid soundbite, “Walls don’t work.”

So what happened after a mile of security fence was erected? Immediately, the number of phone calls about illegal aliens on campus, and corresponding Border Patrol pursuits, dropped to near zero. The number of reports of cartel activity on the tennis courts and parking lots also dropped to near zero. When I was there, I could see for myself how the college campus today is a quiet and peaceful place, free from the dangerous or disruptive criminal activity that dominates the rest of the border.

And what happened to the illegal immigrants and drug smugglers? Did they just disappear or stop trying to come across the border? Of course not. But when they still tried to come over, what happened proved that walls do work.

Most illegal immigrants and smugglers, rather than going over or under the wall, would instead just go around it. This meant that the ends of the wall became “choke points” where the Border Patrol could concentrate its manpower.

But what about the aliens who did try to go over the fence or tunnel under it? After all, the fence is only eight feet tall, and the ground under it is soft and diggable. Nonetheless, the fence was still an effective solution:

Even though the fence added just a few extra minutes to an illegal alien’s or drug smuggler’s journey, that translates to a few minutes for law enforcement to arrive in time to apprehend the criminals. A few extra minutes will change the numerous near-misses like the ones I experienced into actual arrests.

A fence isn’t a magical fix or cure-all. It is a tool that, like any other tool, must be used properly and under the right circumstances to make a difference. It’s just common sense. To argue otherwise is to be willfully ignorant.

But you know who isn’t ignorant about border security? The graduates of the Laredo Community College. They learned all about border security in college.