On Thursday this week, a quarter of a million teen-agers will be up early, anxiously waiting for the post. The A-level results will be arriving, and these 18-year-olds will find out whether they have achieved the grades they need to take up their university offers.

For students hoping to go to top universities and whose places are contingent upon getting three As, the chances are very high that those envelopes will bring good news.

Last year, almost half of all A-levels taken by students at independent schools received an A grade, and the proportion of A grades nationally was 24.1% – twice what it was in 1990.

But their younger brothers and sisters who enter the sixth form in September 2008 or later will have more cause for anxiety. That’s when reforms to the exam system introducing a new A* grade for the brightest will come into effect.

At the same time, students at schools such as Winchester look likely to be studying towards a brand new exam with an even finer grading system called the PreU.

These will help universities distinguish between the “best and the rest”. However, points out Geoff Parks, director of admissions at Cambridge, “Any system which enables more challenging offers to be made will mean more students missing their offers.”

It will seem fairer, though, to more than 5,000 students with three As who are turned down by Cambridge every year and don’t understand why they have been rejected. The A* is likely to mean that universities such as Cambridge make more offers – perhaps one and a half per place, as was the case 10 years ago – rather than “one and a tiny fraction” as they do now, Parks suggests.

In other words, more will be accepted initially, but a greater proportion – maybe a third – could end up at their “insurance” university.

It is too early to be specific about what kind of offers will be made in 2010. It is also too soon to know what proportion of students will be awarded the A*. However at GCSE level, where the grade was introduced in 1994, 6.3% of entries earned A* last year.

Currently, top universities have to rely on preselection by interview and the plethora of special entrance exams which have blossomed as they struggle to pick out the brightest students from the mass of predicted grade As. “We are quite pleased with the proposed reforms,” says Parks.

Not all universities agree with Cambridge. “The University of Bristol is not currently intending to use the A* grade,” says Angela Milln, director of student recruitment, access and admissions.

“Our approach to selecting students is a holistic one which takes account of both academic achievement and potential [as well as extra-curricular achievements].” They are particularly concerned about excluding able applicants from nontraditional backgrounds.

The changes, confirmed last week by government exams advisers, also include a reduction in coursework, with none in many subjects; fewer exams, so more time for teaching; more “stretch and challenge”. This means exams with extended writing in most subjects; more open-ended questions and fewer short answers; and better links between different elements of the course.

The reforms look likely to ensure the A-level’s status as the main university qualification. Many heads of leading schools will agree with Anthony Seldon, of Wellington college, who says, “This is very much a step in the right direction.” He believes it will help address key problems, particularly that the exam does not discriminate at the top end between those who have been well-taught and those who are specially gifted.

Ministers had been urged repeatedly in recent years to institute an A* grade amid concerns about grade inflation and insufficient challenge at the top end. Their delay in acting was one reason many independent and state schools started taking an interest in alternative exams for the sixth form.

Last December, two-thirds of independent schools surveyed by the Headmasters’ and Headmistresses’ Conference (HMC), which represents leading private schools, expressed an interest in the principle of the PreU, which is being developed by the Cambridge International Examinations board. It remains to be seen whether the A-level changes announced this summer will dampen their interest in alternatives.

Unlike the well-established International Baccalaureate, which targets the most able, the new PreU is aimed at the full range of ability. Both are “linear”, which means that students will prepare for one set of exams at the end of their two-year course, rather than for module exams over the two years. The equivalent of the A-level A grade will be divided into four levels of increasing achievement.

PreU students will be expected to study three principal subjects, to complete an independent research report and to present a global perspectives portfolio, where students are encouraged to look at themes of global significance in an open, critical way.

Teachers in more than 50 schools were planning to trial its materials this year. The PreU is still in the process of being accredited by the government’s exams watchdog for use in state schools (such accreditation is unnecessary in the private sector).

Meanwhile, the IB is being taught alongside A-levels at schools such as North London Collegiate and Man-chester grammar.

They are among some 100 UK schools offering the diploma. Wellington will add the IB next year, and King’s College school in Wimbledon believes in it so strongly that it is abandoning the A-level.

The headmaster at King’s College school, Tony Evans, argues that it suits “pupils of considerable ability”. He says, “We like the coherence of the IB’s programme, its academic rigour and its global relevance.”

The general secretary of the HMC, Geoff Lucas, thinks it unlikely that either exam will replace A-levels in most independent schools. Perhaps a quarter will take up each, often alongside A-levels, he estimates.

John Claughton, headmaster of King Edward’s boys’ school in Bir-mingham, has set up a working party to explore alternatives for the sixth form. There has been “increasing frustration with the nature of A-levels” within the common room, he says, adding that AS-level exams have taken the freedom out of the lower sixth. One question the school is asking is whether the wider curriculum of the IB would be better than the spe-cialisation of A-levels. Even with the new reforms, is the A-level curriculum sufficiently challenging?

“At this school, the jury is out,” says Claughton. “Can the same exam be accessible to the widest range and also challenging for the most able? That’s the $64,000 question.”

At the sister school, King Edward VI high school for girls, headmistress Sarah Evans islooking at it differently. “I don’t believechanging the exam system is what changes the quality of education,” she says. What matters is the experience children have, and this should build from the school’s principles. “I don’t want my school’s sixth form experiences to be dictated to by exam boards.”

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