Agreed. Last I checked (don't have a reference right now, unfortunately), Khan Academy was experimenting with a SRS-like feature in their system, in order to tackle this very problem. Everyone tends to forget stuff they're not motivated to use - it's not at all limited to "problem" students.
IIRC, I was told in #lesswrong by a KA contractor or employee that they knew of SRS and some were thinking about how to integrate it.
Post by fellow LW reader Razib Khan, who many here probably know from the gnxp site or perhaps from his debate with Eliezer.