smallwhitecat any Maths teacher on the planet will tell you that out of a total of over £150000, the 50% on what is earned over that amount amounts to a small fraction of the overall amount of pay.
You are thinking of the fraction of overall pay that goes in tax. This is about a third, though will check this on tax calculator in a mo. A long serving teacher with no responsibility points would be on about £34000. S/he would pay around a third also- slightly less.
The difference that the 50% makes is very much a small fraction. I am not a Maths teacher but it's the difference between just under a third and just over a third.
According to the pay calculator
pay £155000 take home £93,019.50 (That's £7,751 per month everybody! Life's a struggle!!)
tax + NI = approx 1/3, bit more
pay £34000 take home £25,482
tax + NI = approx 1/3, bit less
So the 50% rate makes the very small difference between just under a third of your wages going in tax and just over a third of your wages going in tax, ie a small fraction of difference.
pay £22000 take home £17000
tax+ NI = approx 1/4, bit less
Hence the phrase 'the squeezed middle'??
I am sure if there are gaps in my knowledge of fractions here you will put me straight swc but as I say, not a Maths teacher...