Along with never having got round to writing down our constitution and having a monarch who legally owns all the swans, one of the things that makes the UK a bit of an outlier is our university admissions system. In other developed nations, university places are awarded to students on the basis of the grades they achieve in their actual exams. Well, that might work for all those boring nations up at the top end of the OECD education rankings, but where’s the sport in that? In Britain, we do things differently.

Each year when the A-level results come out, thousands of students and their families settle down to deal with the implications – positive or otherwise – of the fact that their actual grades differ from those they had predicted by their schools.

Predicting exam results, like predicting pretty much anything else in life, is difficult

Some people, like myself many years ago, elect to take time out and apply for university the following year, on the basis of the grades achieved. I disagreed with my teachers on pretty much everything, including what grades I was going to get at A-level. I was sure I’d pass, they were convinced I’d fail. The consequence of their poor predictive skills was that I had to spend a year playing basketball, having fun with my friends and saving up for university. So hardly the end of the world. For some, however, now as then, the predicted grades system can be damaging.

Yet schools and teachers are hardly to blame here. Predicting exam results, like predicting pretty much anything else in life, is difficult. Predictably. All sorts of variables and chance factors can affect a student’s performance at exams and the awarding of predicted grades can be affected by personal biases, conscious or subconscious.

As Peter Lampl, founder of the education charity the Sutton Trust, has stated, predicted grades “are wrong most of the time”. Only around 16% of students actually get the grades their teachers imagined they would.

For decades, there have been calls for the system to be changed. For decades, change has been resisted. But last week, Labour announced that if it comes to office, it plans to overhaul the system and bring the UK into line with the rest of the world. Might this be the university administration system’s equivalent of decimalisation? Might predicted grades become one of those strange quirks of yesteryear that the elderly describe to their wide-eyed grandchildren, like old money, the 11-plus and national unity?

Labour is calling for change in light of evidence that the system is not just inaccurate but also unfair. Research shows that predicted grades are more wrong more of the time when the students in question are high-achieving but from disadvantaged backgrounds, disadvantaged being the socially acceptable alternative to a word we don’t like to use – “poor”.

It’s a system that is vulnerable to being gamed by those with social capital and sharp elbows

Research by the Institute of Education at University College London has concluded that almost one in four students from disadvantaged backgrounds who went on to get high grades at A-level (AAB or better) had been predicted lower grades by their schools. And receiving such predictions can discourage poorer students from applying for places at the most prestigious and selective universities.

From daycare to graduation, our education system stacks the odds against the poor. Predicted grades is just one of many hurdles that are set a little higher for those whose parents do not have the money to smooth their path in life or the inside knowledge of how the system works. It is yet another subtle way in which social advantage and parental wealth are able to clog the arteries of social mobility.

Another reason to replace the current system is that in doing so we would spare future generations the strange, life-changing and somewhat chaotic ritual of clearing, the system that matches students with available places after their results are in. We’re told the current system should not be changed because it gives students time to think about their choices and take advice from their teachers. Well, tell that to any of the thousands of students now trying to hack their way through the clearing jungle, being rushed into critically important life choices. Take away predicted grades and you take away the need for clearing.

Defenders of the current system are right to warn that what is being proposed by Labour will involve profound change and resistance to change appears to be the main thrust of most arguments for keeping the status quo. They point out that any new system would most likely require adjustments to both the school exam timetable and university term dates. For teachers, lecturers and administrators, bringing these changes into effect will pose real challenges.

Students (I predict) will find it easier to adjust. We are, after all, talking about a generation for whom the continued existence of polar icecaps, discernible seasons and the Netherlands is not guaranteed. Some tweaking to the exam calendar and changes to the start dates of the autumn term are the least of their worries.

The process of applying for university in the UK, like a first encounter with estate agents, is one of those moments in life when the realities of class and privilege are brought out into the open and thrust into the faces of the disadvantaged.

Predicted grades, along with the personal statement, another questionable part of the application system, and middle-class schools that know how to work the system on behalf of their pupils are all features of an state education system that can entrench privilege. It’s a system that is vulnerable to being gamed by those with social capital and sharp elbows. Anything that makes it a little more fair is surely worth the pain of disruption.

• David Olusoga is a historian and broadcaster