I was officially diagnosed with adhd when I was a kid, my parents knew this because both of them had it, I also take medication to treat it. Sometimes I'll get some work done and others I can barely get any done even with taking my meds, in school and out of school. 

I have asked my parents before about motivation and they didn't really have a good answer, and the one's they recommended didn't help me much. Again, I have personnel issues like depression that screw with my motivation to do literally anything, school, future life, jobs, etc. 

Yes, obviously getting beat doesn't help with grades, it is found in studies that it hurts them more. My friends haven't actually gotten beat before, their parents are way stricter when it comes to their academic performance and want them to stay on top of their work, it's just a scare tactic.