At what point should one give up?

I've tried helping them out by having them shadow me. We agree to break a minute, and then they go missing in action for a while...then just go back to their desk. Even when I know they've done this, part of me feels like I shouldn't have to go get them but that they should be showing interest in learning. Frankly, it's a bunch of time I don't have explaining things as I go when I could just do it. Am I expecting too much to expect that if they want to learn they'll make sure I know they're ready and willing?

They go to meetings that they where not told they had to, good, but then sit in the corner and sleep...bad. I don't even know what to do with that.

Sometimes I give them something small to do and they do it great, so I give them something just a touch harder and they totally fail, hard.

Check in things without testing them.

Part of me thinks that maybe I should be spending more time with them but at the same time I don't see a lot of interest and I really, honestly don't have time teaching the same things over and over. Sometimes I get asked questions that are really, really easy to answer if you just do a little bit of your own work trying to find out. Other times I'm not asked anything.

I'm sure I could be doing better but honestly...I don't really want to anymore.