I think all schools use it in different ways. At my GSs school they subsidize the school bus for PP pupils, I think they pay 50% of the normal price, no one knows unless the child chooses to tell them. The other money provides things like summer school for children falling behind and PP pupils can apply for help e.g. towards music lessons or sports clubs.
At my kids old school the children can bank 50% of the money every year, they are encouraged to do it and then use it for school trips so maybe they wouldn't be able to afford to go skiing in year 9 but 3 years PP money will pay for it or at least make it cheaper, the rest of the money goes on things like revision books, help with computers and internet if families need it.
I think it is a great thing to help kids who might miss out on things. The problem locally, so my kids heard from classmates, is some business owners, often farmers locally due to where we are, pay themselves a very small wage while living in a beautiful farmhouse, kids have ponies and a great standard of living but still get free school meals and PP help. One child we knew had a father working abroad, mother claimed benefits as a single parent and child got all the help going whilst also getting holidays round the world, expensive presents and every advantage going, she actually told my kids we were stupid to pay bus fares and school meals when you could get it all for free. I guess every system can be exploited and better that some get things they shouldn't rather than the kids it is intended to help miss out.