Honestly, I don't think the physical punishment for wrong doing is the right answer at all.
My dad used to paddle me with a wooden... thing... with holes drilled through it. He did that all the way up to like 4th grade. He stopped paddling me because I was starting to get almost as tall as him, and I was starting to develop. After that it just turned into yelling and screaming when I did something wrong or dropped down to something like a low B in school.
At this point, even today, say I... didn't make my bed before I left for work or my desk is a mess because I was trying to find some cables or something the night before. I get a nice long (ignored) lecture about how my room is a pig-sty and I wasn't raised to be a slob when I get home that night. Even for little shit, like say I leave a cup on my desk, or some other minor thing that only I have to deal with; I get either lectured about it, or yelled at.
I can tell you this from MY perspective: I just don't give a **** anymore, point blank. Most of the time I just lean up on something and stare vacantly behind my dad's head and just say 'uh huh' when he pauses expecting a response. I just repeat that until he leaves... and it seems to work. I made the mess, I have full intentions of cleaning it up, I don't need to hear about it every time I do something deemed 'wrong'. If I've done something wrong, there's a GOOD chance I realize what I did, and I'm going to do whatever I can to correct the problem.
What I'm trying to convey here, is too much 'punishment' is not going to solve anything. I realize I've fallen under the statistic, but it's just how I feel at this point, truly and honestly. I don't care. Granted, I'm 19, and I know my dad is trying to make sure I don't do stuff like this on my own once I get out of the Navy, but damn. I'm sick of hearing the same old song and dance OVER and OVER again. I get slightly angry and annoyed when I hear the light switch in the hall firmly smashed up to turn the hall light on, and my dad's heavy trodding steps on the carpet up to my door at this point. When I hear that, I just hit pause on whatever I'm watching, mute the TV, or shut the screen off on my computer and turn the speakers off. Then I just unlock the door (I lock it, because otherwise he barges in multiple times through the night for stupid stuff), sit back in my computer chair, and prepare to drift off into bliss.
You have to see what's causing the issue in school with your son. Talk to him about girls, if he's starting into that stage yet. Wander onto the topic of bullies, anything you think could either be getting at him. Hell, he might just be thinking that it's getting hard in school, and he doesn't want to do it anymore. Just talk to him about how it's something we all went through, and no matter how hard it seems, don't give up because it pays off in the end. My dad always uses(d) the same quote with me: "Do you want to end up with a job where you have a name tag on your shirt, asking 'You want fries with that?', or do you want a job you like?".