In brief, the issue of segregated proms goes against the constitution which is the foundation of the country. In Plessy v, Ferguson, the Supreme Court ruled that the Fourteenth Amendment provides equal protection which prohibits racial segregation. This includes any form of segregation such as in proms
It would be a "proportional" tax rate system that uses the same rate for all income levels, although in most western countries this is not used. Instead a "progressive" tax structure is used.