学校禁用手机：有用，但见效慢
Banning mobile phones in schools has become hugely popular around the world. But the largest study yet suggests the benefits may take longer to appear than many people expect.
Researchers from Stanford and three other American universities looked at more than 43,000 middle and high schools across the United States over three years. They compared schools that required students to lock their phones in special pouches for the whole school day with schools that did not.
The bans worked in one obvious way: students used their phones much less during school hours. However, the effect on test scores was close to zero on average. There was also little change in attendance, attention in class or online bullying.
The most interesting finding was how things changed over time. In the first year after a ban, discipline problems actually rose and students reported lower wellbeing – perhaps because they were frustrated at losing their phones. By the third year, however, discipline had returned to normal, and student wellbeing was higher than before the ban.
One of the researchers said phone-free schools were "not a simple or quick fix". Another described the study as only a first step. The message for schools seems to be that patience is needed: the benefits of a ban may only become clear after students have adjusted to it.
在学校禁止使用手机，如今在世界各地都很流行。但迄今规模最大的一项研究显示，好处显现出来所需的时间，可能比很多人想象的要长。
斯坦福大学和另外三所美国大学的研究人员，对全美 4.3 万多所初中和高中进行了为期三年的研究。他们比较了两类学校：一类要求学生整个上学期间都把手机锁在特制的袋子里，另一类没有这样的要求。
禁令在一个方面效果很明显：学生在校期间用手机的时间大大减少了。不过，它对考试成绩的影响平均来看几乎为零。出勤率、课堂专注度和网络欺凌也没有什么变化。
最有意思的发现，是情况随时间推移发生的变化。实施禁令的第一年，违纪问题反而增加了，学生的幸福感也下降了——可能是因为不能用手机让他们很不满。可是到了第三年，违纪情况恢复到了以前的水平，学生的幸福感甚至比禁令实施前还要高。
一位研究人员说，学校禁用手机“不是一个简单、快速的解决办法”；另一位则形容这项研究只是迈出了第一步。对学校来说，关键似乎在于耐心：禁令的好处，可能要等学生适应之后才会慢慢显现。