Teachers will be able to get an instant analysis of how their pupils fared in each A-level and GCSE question when results are published later this month.
In another example of how computers are transforming England's exams system, the Edexcel board is making the service available for subjects sent for marking by examiners electronically this year.
On the days that the results come out (A-level grades are released next Thursday) teachers will be able to log on to a secure website and see the average mark for their school's pupils in each question of a particular paper.
They can then compare this against the national average for all pupils on that question. They can also contrast the results between different categories of schools, for example selective secondaries or comprehensives.
The website will give schools an early preview of chief examiners' reports in particular subjects, offering them the chance to compare their results on a question with expert views on how students across the country answered it.
The service is being made available by Edexcel only for the 44 papers, in subjects ranging from A-level biology and maths to GCSE French and science, which were marked electronically this year.
Students' scripts were scanned on to computer and marked on-screen by examiners in a trial that will be extended to other subjects next year.
The instant analysis is possible because, unlike exams which are marked traditionally, marks are fed into the computer system question-by-question as they are awarded by the examiner, subject to review by senior colleagues.
The board believes the service will help schools make more informed judgements about what is and is not being taught well. Jerry Jarvis, Edexcel's director of general qualifications, said: "You may, for example, find that your students did not answer questions two and three on a paper very well, but that, nationally, the answers were good.
That may lead the school to come to conclusions about the way that area of the syllabus was being taught. There may be areas where they need to improve."
He conceded that this could place teachers' performance under increased scrutiny, but said most would appreciate the chance to analyse the strengths and weaknesses of pupils' knowledge.
Gwen Evans, joint deputy general secretary of the Association of Teachers and Lecturers, said: "This may help teachers, in that it could inform how they deliver future courses for pupils. But it also has the potential to raise the pressure on both teachers and markers, and to increase still further the influence of examinations on what is taught in school."
Teachers can get a preview of how the new service will look at www.edexcel.org.ukquestionlevel