Quote from TofuQueen

#2 - If anyone had a real solution for this, they'd write a book and it would be on the best seller list constantly. In my experience kids who don't care, don't care, and until something happens to make them care, they just won't. They know all the stuff about throwing away their future blah blah blah but it's not real to them, or they think they'll get around it, or the lure of doing something else is just too strong, or whatever.

Quote from practically everyone

What does she want to do with her life?

There's your winner.

Step two is identifying the precise 'consequence' that'll spur her motivation.

I mean, you can shower her in Tinny-kins' envious tears until your red in the eyes, but I find that's about as effective as teen-moms preaching abstinence/protection to sex depraved teens. It'll work. Sometimes. But there's alway gonna be that one ho who thinks her eggs are sperm-proof, or that one man-ho who thinks he's the only dude in the universe who's perfected "pulling out". I'll try to keep it fair.

Anyway, just plain smothering her ain't cuttin' it at this point, and sometimes colossal failure is the best supplement for self-motivation.

The problem being that your idea of "failure" differs from your sister since you presumably have a goal, and I'm guessing your sister has no plan after graduation. "Go to college" isn't really a goal if you have no reason for going in the first place, so don't give her garbage about that; she doesn't care. Attempting to coax a career path outta her might seem like a fruitful plan, but if she's like me, she might not have the confidence to pursue it, or think it's a field she'll never "break into", all the way to the point that you'll only get the ol' runaround when you ask. Which is similar to rychels's C statement, but a little different.

Like DorkFishOK was saying, there might be a million other things to look at too. Has this always been a problem? Is she outgoing? Timid? She have a lot of friends? A social outcast? What's she normally do after school? Go out? Stay at home? Is she generally happy? Sad? Rebellious? Does she even care?

Too much to consider. I suppose I could recommend one of my co-worker's "universal methods": Destroy her comfort. Break the shit she loves, and tell her to get a job if she wants to get it back.

...Please don't do that, but maybe her getting a job right now could break in the reality that she'll have to earn her own way, someday.

Crenshinibon raises a good point too, which you may not like, but as Maddox would say: "someone's gotta bag my groceries." Or a trade. Either or.

Whatever the case, good luck.

If you were my sister, I would hate you to the core. You physically tried to sit her down? At least my sister had the sense to keep her hands off me. I once suffered from lack of motivation and I resented it when my sister tried to help me. My parents were already on my case and I hated my older sister for interfering and thinking she had some authority over me. Even if I understood deep down that she cared about me, it hurt what little pride I had. If your sister hasn't listened to you by now she probably never will even if you change your approach. I wouldn't take on a parenting role unless your parents are totally irresponsible.
That aside, I agree with "practically everyone" and badkarma.

Looking for... shoujo with a canned peach confession. Don’t English me I’m panic.

Positive reinforcement is good for getting children to do what you want. If you want it to last, it's better to use partial reinforcement as opposed to continuous reinforcement. Effectiveness will be affected by your relationship with your sister so if you're not on good terms with her, get someone who is to do it. This doesn't get to the root of the problem, but it buys you time and hopefully, your sister will actually mature by the time this becomes ineffective.

You probably just need to remove yourself from the equation. Also, your presence in having the child do her work has encouraged her to stop doing her work, because you will be there when you might not be there otherwise.

To tell you the truth, negative reinforcement works well. Negative reinforcement is when you remove something (such as yourself) from the environment. Positive reinforcement is when you add something (such as punishment or praise) to the environment. Positive reinforcement normally encourages behavior and negative reinforcement discourages behavior.

So, remove yourself (don't talk to her (negative reinforcement)) and praise her when she finishes her work (positive reinforcement).

This might help

[color=green]"Officially, this machine doesn't exist, you didn't get it from me,
and I don't know you. Make sure it doesn't leave the building."[/color]

Thanks for all the suggestions guys. I'm especially thankful for the huge blocks of text. I was afraid I'd get a lot of unhelpful replies basically telling me I suck. 🤢 But for the majority, they're really helpful.

And I think you guys are right - it's probably because I'm not her parent, and am in fact only 2 years older then she is. And rychels, I think that might be it as well. Sometimes when I try helping her with her homework I do get the feeling she doesn't actually know how to do it but is ashamed of that as well, and doesn't want to admit it or let me help her. She also does spend as much time away from home as possible, hanging out with her friends and whatever else she does. So it might be something similar to Blueharro's situation, where she just got into this downward spiral and now is just trying to avoid grades and the pressure that comes with them altogether (it does seem that the longer she's been in high school, the lower they go down)...So it's just one great giant pile of shit.

I guess I'll try taking myself out of the equation, and just ignore her grades for a couple weeks. Hopefully it'll work?

Again, thanks so much guys! Not only for your awesome, well-thought out responses but also for listening to me whining.

Does the walker choose the path, or the path the walker?