In which case you may like how it’s done in the UK. it’s technically debt but in essence works as a graduate tax. The government pays for your education with a loan. You then only pay back 9% of your income over a certain income threshold. You do this until you pay back the loan or 30-40 years have passed. So in practice this is a graduate tax.
Australia does something similar (it's called HECS if you want to search for details).
For most taxes you expect higher earners to pay more but this is not the case with student loans because high earners pay of their loans quickly whereas lower earners end up paying far more in interest.
An actual graduate tax would be far less regressive than the current system