Sixth-formers across the country are waking up to their A-level results which have been determined by teachers after this summer’s exams were cancelled.

Hundreds of thousands of students in England, Wales and Northern Ireland are receiving grades to help them progress on to university, work or training, with some experts predicting that “inflation” may occur this year.

Last year, nearly two in five (38.6%) of UK A-level entries were awarded A or A* grades – a record high – following a U-turn over grading, compared to just one in four (25.5%) in 2019.

If more students gain top grades – which are being submitted by teachers after exams were cancelled for the second year – then it will be more difficult for top universities to differentiate between applicants, it has been suggested.

Youngsters who miss out on the grades needed to meet their university offers are likely to face greater competition for a place at leading institutions as there could be fewer selective courses on offer in clearing.

But unions representing school leaders and teachers have urged parents and students against using law firms to challenge their results – and appealing against grades just “for the sake of appealing”.

This year, teachers in England submitted their decisions on pupils’ grades after drawing on a range of evidence, including mock exams, coursework, and in-class assessments using questions by exam boards.

Dr Mary Bousted, joint general secretary of the National Education Union (NEU), told the PA news agency: “Parents should be really warned not to hire lawyers to make the case for a different grade because it will impress no one, it won’t impress the exam boards.”

She added: “Dressing up an appeal in legal language is not going to bolster that appeal, or make it more likely to succeed. So if you don’t want to waste your money, don’t do that.”

Paul Whiteman, general secretary of school leaders’ union NAHT, told PA: “There is certainly a worry that we are going to face more appeals than normal, but we just don’t know yet.

“Although the appeal system is there to bring a further level of confidence, spurious appeals or hopeful appeals will probably be a waste of time because the system that’s been brought in is a robust system for this year.”

Dressing up an appeal in legal language is not going to bolster that appeal, or make it more likely to succeed

He added: “My only appeal to students and students’ parents is that a lot of work has gone into this assessment, you should be able to rely upon the assessment so simply putting an appeal in for the sake of appealing in the hope that your grade might move would be the wrong thing to do.”

Geoff Barton, general secretary of the Association of School and College Leaders (ASCL), said “legal firms turning themselves into ambulance chasers and saying to parents for a certain fee they will run an appeal” was unhelpful.

He said: “That seems to me incredibly misguided because appeals are there for anyone who wants to use them, but they’re based on two things: did the school follow due process, and was the grade awarded a fair grade. That will be down to the awarding organisation.

“If you’ve got a concern then the process is there, but you really don’t need to be sending money to lawyers.”

The Department for Education (DfE) has said all A-level grades have been checked by schools as part of a quality assurance (QA) process – and one in five schools had a sample of their grades checked by exam boards.

Last summer, the fiasco around grading led to thousands of A-level students having their results downgraded from school estimates by a controversial algorithm before Ofqual announced a U-turn.

This year there will not be an algorithm used to moderate grades.

Nick Hillman, director of the Higher Education Policy Institute (Hepi), said it could be more difficult to get on to a top course this year if grades are missed.

He told PA: “It could be harder to get in than usual if you fall a grade or two behind your offer and if it is a competitive course.

“My advice would be to act swiftly if you need to find a place somewhere else.”

An analysis conducted by PA suggests that the day before results were due to be released, for applicants living in England, there were more than 26,000 courses with availability.

It shows that, as of Monday afternoon, 14 of the 24 Russell Group universities had vacancies on courses for English residents – around 2,390 courses between them – on the Ucas clearing site.

It could be harder to get in than usual if you fall a grade or two behind your offer and if it is a competitive course

The numbers of courses listed change frequently as different courses are filled, or become available.

At the same point last year, the day before results day, 17 of the Russell Group institutions had around 4,485 undergraduate courses listed on clearing with potential availability for students in England.

Last week, the head of the admissions service warned that clearing is likely to be “more competitive” for students seeking places at selective universities this year due to uncertainty on teacher-assessed grades.

Clare Marchant, Ucas’s chief executive, urged students receiving their grades to make a decision “in a matter of days” rather than waiting weeks.

But she added: “On Tuesday, I am expecting to wake up and have record numbers with their first choice.”

Last week, the Medical Schools Council (MSC), which represents 44 heads of medical schools across the UK, warned that some schools may still struggle to increase the number of students they admit despite the announcement that medicine and dentistry schools will receive funding to expand courses.

Students who want to study medicine will have the option to defer their places until next year or choose to move to a different medical school amid capacity constraints, the MSC said.

Kate Green, Labour’s shadow education secretary, said: “Students have worked incredibly hard in extraordinary circumstances and should be proud of the results they are receiving today.

“They have done this in spite of a Conservative government which has let them down at every turn and shown no ambition for their futures.”

Education Secretary Gavin Williamson said: “Students have worked very hard in what has been an extraordinary and challenging year, and each and every one of them should feel incredibly proud of their achievements. We should all celebrate their resilience and ability to overcome adversity.

“Teachers and staff have ensured that, despite the disruption caused by the pandemic, all students are able to get grades this year and so can take their next steps and make their choices about further study or entering the workplace.

“I am hugely grateful to teachers and also parents for supporting our young people in progressing to the next stage in their lives with confidence.”

In Scotland, high school pupils will also find out their exam results on Tuesday, the second time they have been upended by the pandemic.

The Scottish Qualifications Authority will release results at 9.30am, with pupils being notified throughout the day.