This year's A-level results are published later this month

They feature fewer units of study and and more open-ended essay questions, as well as an extended project.

A new A* grade, recognising the very high achievement of those gaining more than 90%, is also being introduced.

The Qualifications and Curriculum Authority said they would equip pupils better for work and further study.

We want young people to be challenged to the limits of their capacity Ken Boston QCA chief executive

Schools and colleges will begin teaching the new courses in September 2008, with the first AS-levels being awarded in 2009 and the first full A-levels in 2010.

The changes take place across England, Wales and Northern Ireland.

Chief executive of the Ken Boston said the A-level was a high quality and demanding qualification which deserved its international reputation.

"The reduction from six to four units in the majority of A-levels will require students to show greater depth of understanding of a subject across a range of questions.

"The introduction of an extended project will require them to demonstrate the skills of planning, preparation, research and independent working.

"Candidates will be required to justify their work and explain how they reached their outcomes. The project is also a requirement of the new Diplomas."

He added that the introduction of an A* grade would reward exceptional performance.

Brightest pupils

"We want young people to be challenged to the limits of their capacity, and recognised when their achievement is outstanding," he said.

The A-levels review took place after some complained the exams were getting easier.

Universities also said they could no longer use the results to distinguish between the brightest pupils.