I am certainly no expert with regard to the solution you seek, but perhaps your students (at least the first you described) might have a condition identified as Undifferentiated Attention Deficit Disorder. Google the condition for which I found a description/symptoms as well as remedies (kidsource.com was one of several sources). At a minimum however, I would discontinue the use of video games, movies etc. which the student probably sees as more for entertainment than for learning.
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