The mere presence of a cellphone negatively impacts cognitive performance regardless of its power status. The brain has to use energy to not think about the phone now that the addictions are so strong. This is quite concerning.

> Researchers at US universities including Stanford and Duke looked at nearly 1,800 US schools where students’ phones were kept in locked pouches and found little or no differences in outcomes compared with similar schools without strict bans.

It's worrying that as many as 1,800 schools are already using locked pouches. Parents are forced to foot the bill for the pouches, at inflated prices because the provider will have an exclusive contract with the school. There's a massive bottleneck at entrance and exit times, so kids are forced to wake up earlier, with detrimental effects on concentration. Plus it prevents phones from legitimate uses, such as emergencies.