Yes, and identical twins raised apart show extremely similar academic achievement, far more similar than non-identical siblings raised in the same household. This strongly indicates that academic achievement is highly explained by genes but that recombination [1] causes enough scrambling to result in large variance among non-identical siblings.

[1] https://en.wikipedia.org/wiki/Genetic_recombination

Sure, and they may not all have the same colour eyes - variation is expected.

But still, we have nature (genes, 60-70%) and nurture (hey, parents again). What else is there?

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.

Luck (excluding controllable factors by wealthy parents)