If you attended elementary school in the 1970s or 1980s, you probably had open classrooms. This meant that there were no walls—except for the chalkboards and cabinets that teachers shoved into position to define the space. The idea was that it would make it easier for teachers to collaborate, although this rarely actually happened. But it meant you could hear pretty much everything that was said in every class around you. It was distracting—and educationally useless. In other words, it was yet another in the long line of well-intentioned but pointless educational trends that had its heyday and then was consigned to the footnotes of history.

In a day when a new tool and app that promises to revolutionize education completely comes along on an almost-daily basis, it can be hard to see past the hype and remember that most educational trends last about as long—and have about as much effect on the wider society—as most fashion trends. There is no solid, empirical reason to believe that this is no longer the case now that students have their own devices.

Rather, emerging educational technology has several significant drawbacks that educators and thought leaders need to understand. As already mentioned, the history of educational trends and educational technology does not suggest that most experiments will work well. Rather, once the wheat is separated from the chaff, we are likely to find that only a few ed tech options have real benefits and thus real staying power.

Second, it’s time to think about opportunity costs. A child who spends twenty minutes selecting fonts and colors for a presentation is not engaging in critical thinking, collaborative learning, or any of the other twenty-first century skills that educators are so intent on developing. Rather, they are just wasting instructional time.

It’s also well past time to think about the opportunity costs of new technology. Even the simplest app or tool requires some professional development, some troubleshooting, and some tech support. All of those resources are finite—in most schools, they are in fact constrained. An edtech tool might be free, but if the staff costs are high, it is no bargain at all.

Finally, educators would do well to remember that technology immersion shapes the brain. They need to be careful that videos and interactives don’t crowd out reading, a skill essential to every child’s future.

In short, it’s time to count the costs of ed tech.