Motivation is one major tool to raise the level of arousal.
Motivation: If in our judgement there is no compelling reason to attend to something, we probably will not put much energy into it. Here, of course, we are partly talking about arousal again.
When I appear, as I often do, in front of my on-campus class acting somewhat crazed, dressed in a sumo outfit and brandishing a spear, I usually get the full attention of the entire class.
Those slumped over their desks in the first row raise their heads (become focused) and watch (sustained focus) for a while, until the police came (selective and divided focus).
There are, of course, better ways of motivating students. Providing grades is one, if not a rather weak motivator.
The principal of feedback is sound, but the time lag and lack of significance of a letter or number grade is questionable.