So someone who got a benefit from the state that addresses a serious, well-proven injustice, and wasn't crawling on their knees and begging for it. Sounds like the system is working.
Even if your anecdote is real, and their use of an Audi indicated they were well able to pay full school fees, so what? We give such benefits to the parents because we want to target the child. Sometimes the parents might make different financial choices, obtain a car that's more than they need. (And you don't know how they got it, whether it's used, or whether they feel they need it to "keep up appearances" with others so peers, like you, don't judge them by their car.)
In any case that's why the benefit is delivered as reduced school fees. TLDR the children aren't the ones who bought the Audi.