Luck (excluding controllable factors by wealthy parents)

I'd say opportunities. When there are fewer kids matriculating into college it's easier to get into a better school (see Malcolm Gladwell's Outliers)

Professors and Teachers, the variability of them is huge.

Friends can have a huge impact as well. Is the norm to skip classes to go work on a startup or focusing on getting good grades?

Resources such as the Numberblocks which make math more visual and accessible. My pre-K kid was doing multiplication because of that show.