Lee wrote, "Think about the average length of a regular school or college class—roughly 60 to 90 minutes. Numerous studies stress that the average student’s attention span is 10 to 15 minutes. It also depends on the time of day, the weather, how the student is feeling that day and other factors. That means that a teacher has a very short window to grab that student’s attention and hold it or they’re gone."
I Lee identified the issue; schools are designed with long blocks of time which are not used effectively. If the teacher expects passive learning, then the students, who wish to be active, will check out.
Lee also acknowledges that adults do multitask all the time, "In moderation multitasking is perfectly normal and can even be somewhat productive." The challenge is teaching students how to multitask in moderation.
Lee writes, "...mindful “task switching” (which is probably a much better term for what we call multitasking.) The goal should be to find ways to balance continuous partial attention with focused concentration."
I would propose that if students are allowed to pursue passion-based projects, take part in active learning, and engage in their interests with voice and choice on how they demonstrate their learning, then they would find moments of focused concentration and mindful task switching would be minimal.