Here's the math:
Warren tax = 0 on first $50m + 2% on next $950m + 6% on the rest
Bezos is so rich (net worth ~$275b) that only the last number matters, and it comes about to about $16.4b.
There are 3.8m teachers in the US, making on average $74k/yr.
16.4b / 3.8m = ~$4.3k
4.3k / 74k = 5.8%