Tis the season to be jolly. But not if you’re one of the thousands of children sitting crucial public exams in January. For them it’s the season to try to nervously swot up, no matter how alluring the pull of parties, presents or boyfriends and girlfriends.

It’s a dilemma 18-year-old Caoimhe Byrne understands. This time last year Caoimhe, who is hoping to study law at university, was facing three exams, comprising a big chunk of her economics A-level, and all three in the new year. For, since changes to the curriculum seven years ago, many AS and A-level exams are now held at the start of each year, with the rest scheduled for the traditional summer months.

So how did Caoimhe cope with being swotty rather than jolly last Christ-mas? “Obviously it’s the festive season, and that’s what I did for the first week of the holidays. I went out with friends and enjoyed going to parties.”

But in the last week of the vacation, straight after new year, Caoimhe’s parents, who live in Reading, booked their daughter on to a residential Christmas “crammer” course in Oxford, one of the dozens that have mushroomed across the country since the advent of January exams.

“At first I thought going away over the Christmas holidays for a week to revise was going to be terrible,” recalls Caiomhe, who is also taking A-levels in history and physics. “But everyone was sociable in the evening. In the daytime I was in a small class focused on the modules I was studying. It got me back into exam-thinking mode.”

Caiomhe scored two Bs and a C in the exams she had revised and is this summer retaking one to boost her grade – another advantage of sitting them first time round in the new year.

Mario Peters, principal of Oxford Science Studies, where Caiomhe studied, says he expects 200 teenagers to enlist on his revision courses, which cost £350 for three days, later this month. “It used to be unusual to put on revision courses at Christmas,” he says. “They were always at Easter for the summer exams. But the advent of January exams has changed things.”

For high-flyers, says Peters, good results in January exams are crucial because universities now ask to see AS results achieved in the first year in the sixth form. As a result, for students pursuing competitive fields such as medicine and law, anything less than a string of A grades at both GCSE and AS-level can damage the likelihood of being offered a place.

But with courses across the country costing hundreds of pounds for a few days’ tuition, how can parents decide which will give their child a genuine chance to boost exam grades?

It’s the same problem parents face when they choose Easter courses. Horror stories flourish in the loosely regulated revision market, which also includes private tutors charging upwards of £20 an hour for tuition.

Ori Leslau, now 18, had an encouraging experience when he sat his GCSEs in 2005. Teachers at his private school in north London had predicted that he would achieve only an E grade in science, so his parents booked him into the Mander Portman Woodward college in the capital over the Easter holidays, which they’d been told about by friends. For Leslau, the one-week £550 revision course in a small class, boosted him up to a C in science when he took his GCSEs a few weeks later.

But a friend of Leslau’s, who signed up at a college with classes of up to 30 students, also in the capital, complained that “it was like being back in school”. His friend’s final grade in GCSE science was a letdown.

Stephen Palmer, director of the coaching psychology unit at City University in London, says parents should ask colleges for the grades achieved by the students they cram as well as testimonials from and phone numbers of previous students. They should check that the colleges are teaching the right syllabus and that the class sizes are small.

“Parents need to get proper feed-back from these organisations,” says Palmer. But, he adds, parents may be able to do as good a job themselves if they take the time to help their child with revision and going through past papers. “If parents can be bothered to sit down with their child and help them that is better than anything else. Parents need to take more responsibility rather than farming their child out to another expensive organisation to do the work.”

And as for Christmas revision, Palmer says: “Youngsters must have some time to relax. There should be no working on Christmas Day – or New Year’s Eve, either, for that matter.”

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