with the U.S.'s graduated tax rates, the top 20% of earners, who are probably disproportionately college graduates themselves, pay almost 90% of all taxes. I don't like either this particular policy or the student loan regime overall, but I also think it's somewhat inaccurate to characterize it as construction workers subsidizing bankers. Bankers subsidizing teachers is probably closer to the truth.
The Top 20% of earners also make all of the money.