This week Cambridge University confirmed that from next year, three A-Grades at A-Level (the exams British school children take at 18) would no longer be enough for a student to be admitted. In future, students will need at least one A* and two As to be considered for a place.

There have been predictable complaints about this, with some arguing that such an admissions procedure will discriminate against students from state schools. But what did the government expect when they introduced the A* grade? If universities weren't meant to use it to distinguish between students, then what was the point?

Moreover, it's not exactly the university's fault if demanding a top grade means only people educated in the private sector can get in (though that is clearly an overstatement). On the contrary, it's the state schools, and by extension the politicians who believe they can run them, that deserve to be the targets of criticism.

It is also politicians who have debased the exam system and made the introduction of an A* necessary. As the Telegraph says, "Last summer, more than a quarter of A-level exams sat in England, Wales and Northern Ireland were awarded an A grade and the rate has more than doubled in 20 years." Grade inflation is not that different from monetary inflation – by increasing supply for political reasons, government agencies have decreased value. It seems they just can't help themselves.

The other thing that irritates me about this story is the implication that lies behind it, that requiring excellence (if that's what an A* means) is some kind of unjust discrimination. It isn't. Rewarding achievement and success is the way the world works, and rightly so. That's all Cambridge are doing.