An apple a day

In school, there was always that one kid who’d bring the teacher apples.
That kid was me.
“Thank you,” the teacher would say. And she’d eat the apple. “Delicious.”
I was a smart kid, and I got good grades on my own.
But I’m sure the apples helped.
Until one day I got a bad grade for something.
That’s when I mentioned that the first apple had poison in it.
“And the other apples have a temporary antidote.”
From then on, I got good grades.
And the teacher got the full antidote on the last day of class.
I think.