School's out. Now, for a summer before a mind-dimming smartphone.

As a teacher in the Minneapolis School District, I've dreaded summer vacation. I know my students well, and I know that for many, the summer will be spent in the pallid digital haze of the smartphone or video game. In other words, I dread the negative effects on their young minds from spending most of their free time staring passively at a screen rather than engaging in the real world.

The stakes are high, because their behaviors, what they habitually do, physically alter the inside of their brains. In an eye-opening study, the Journal of the American Medical Association says, "Exposure to excessive screen time has been associated with a variety of negative outcomes for children." This includes problems with attention, learning, lower academic performance, obesity and negative behavior.

I could cite a lot of disturbing research on this issue, including how violent video games drain kids of their capacity for empathy, but let's just talk about what we all see, and let's acknowledge how uneasy it makes us.

Smartphones dominate our children's lives, and they are a blight in the classroom. I have a ban on electronics in my classroom, but I see students who begin to twitch and fidget within seconds of putting their smartphones aside, because they can't resist them. They simply do not have the mental strength to resist picking them up to begin gazing, clicking and swiping. Every two or three minutes when they look at that smartphone again, their attention is completely lost to everything around them, and their minds can never fully engage. This is not some silly teen fad. There is an element of desperation in their constant interaction with these devices as if in need of some profound emotional comfort. I'm not kidding; it's a bit disturbing to witness.

I'm an English teacher, and I try to teach my students how to engage with complicated texts on a deeper level. It requires concentration. The mind needs uninterrupted focus to wrangle with higher-order concepts. As adults, we've all probably had the experience of chewing on a hard intellectual problem for a while until we arrive at that "eureka!" moment. I try to create lesson plans that manufacture those moments for my students, but smartphones are my enemy. During a lesson, students are constantly sneaking glances, and their concentration is destroyed.

To state the obvious, teens are easily distracted to begin with, but the digital distractions are more pronounced, more disruptive and more destructive to their intellectual processing. Some of our nation's top engineers — brilliant people from elite universities and Silicon Valley — are working tirelessly everyday to figure out how to distract your child through software that pings and buzzes and flashes. Our children don't stand a chance.

You can bet I've confiscated many phones over the years, and the reactions from many of my students are shocking. They get angry. Red-in-the-face anger. Some will look me in the eyes and with a threat on their tongues say, "You don't touch my phone." It always reminds me of when we took away my daughter's pacifier when she was a baby. She howled at the loss of her pacifier, and I can't help but think that smartphones are infantilizing teenagers in a similar way.

I've heard horror stories from my students who have seen brothers smash TV sets when their parents demand that they stop playing video games or who have spent entire weekends — sometimes 30 to 40 hours straight — playing video games. Teenagers can't handle it. They don't see how manipulated they are by the technology. When you attempt to separate them from their devices, they become surly and panicked and lash out at you, which is an indication of how deeply the tentacles of technology have infected their brains.

I'm calling on all parents to do four things:

• Confiscate phones and laptops at, ideally, 9 p.m., but certainly no later than 10 p.m. Nighttime is the most dangerous time for kids and their use of electronics. If they tell you they don't use them at night, they are lying. Be firm. Do not back down. I am psychically sending you strength right now, because kids who are especially addicted to electronics will fight you on this. Be prepared for this to be a siege that may take a few days. Have a plan to outsmart them before you take your stand.

• Have an electronics-free period of every day.

• Model restraint with your own electronics usage. I only use my smartphone as a tool. Unless we are FaceTiming with grandma or getting driving directions, for instance, I put the device away.

• Have an electronics vacation. Just spend some designated time — three days, a week, whatever — without electronics. It is liberating.

The pervasive use of smartphones in our society is a relatively recent phenomenon. If you want to see the early indications of what smartphones, in particular, are doing to our children, look how closely the trends for increased smartphone use correlate with the decline of both ACT and SAT scores. I can't draw a causal relationship between these trends, but as a teacher interacting with hundreds of teenagers on a daily basis, let's just say I have my suspicions.

So, yes, I've dreaded summer. I went into teaching because I care about children. I want them to lead fulfilling lives, and I want them to contribute in positive ways to society. But I know that in the fall I have to face students who have averaged more than 40 hours per week interacting with electronics, smartphones and video games, "more time than they spend in any other single activity except sleep," according to the JAMA article.

As a teacher, I can see firsthand the damage technology is inflicting on our children. This is no small issue, and as a society, since this issue is so new, we are just beginning to recognize it. As a parent, for the sake of my kids, I can't afford to wait.

Thomas Johnson lives in Minneapolis.