rant:
Child abuse is not something to just throw into a story to make a character's life horrible or give them a tragic backstory. When I say "throw into the story" I mean having a character come home and everything is fine and for literally no reason, like the parents aren't drunk or anything and they have no reason to be upset, just beat the kid to a pulp.
If the parent is going to barge in and beat the kid, they are probably drunk, and/or something happened to make them upset (maybe the kid didn't do something or something happened at work) but if they really just use the kid as a punching bag with no rhyme or reason, just to punch THEY DONT LET THE WORLD KNOW ABOUT THE KID.
If we are talking mental-illness with the parent/guardian to the point of beating the kid for no actual reason, just for their enjoyment, then they wouldn't do things like let the kid go to school, or even let them out of the house. They would probably lock the kid in the basement.
Child abuse can be written well, and accurately, but if it's just something that happens for literally no reason and youre just throwing it in there, then it can be offensive to people who have gone through child abuse - youre making it seem like it's just some throw around character building with no heart behind it - and it can be weird to read, leaving people going "what just happened?"
I know what it's like to go through a part of my life with a borderline-abusive parent. Speaking from experience I only got lashed out at when I did something that made them upset; like cry.
It's not big things that have to set these kind of parents off, but something has to set them off, unless the kid is locked up and is a personal punching bag (and lets be honest in this case, probably a sex toy as well), then something had to have happened.
Also, usually parents dont think these things through, its an act of anger (sometimes inviting drugs/ alcohol) so just keep these things in mind while writing please.