While the promoters of the poll tax pretended it was equitable (everybody uses the same, so should pay the same), the poll tax was (surprise) a significant subsidy by the poor of the rich, because the middle classes do, in fact, make more use of locally funded services than the poor, particularly education.  Middle class children are more likely to stay at school beyond 16, and go on to university.  And at that time your university fees were paid for by your local authority, even if you received no maintenance grant.