There was a rise this summer in the number of students in England taking traditional GCSEs and A-levels, the exams regulator, Ofqual, says.
Provisional figures show entries for English, maths, science and computing qualifications increased.
Ofqual says the rise is likely to be in response to government targets for more teenagers to study academic subjects.
However other subjects, such as citizenship, saw a decline in exam entries, Ofqual said.
Ofqual also noted decline in the number of students taking modern foreign languages.
Chief regulator Glenys Stacey said: "The subjects that are proving to be more popular this year are the traditional ones.
"There's been a drop-off in subjects that have never been high-volume ones anyway and there are one or two noticeable subjects that have dropped, for example GCSE citizenship studies where we've seen a 50% drop in take-up."
The data suggests government performance measures, such as the English Baccalaureate (EBacc) - where pupils have to study English, a language, maths, science and history or geography at GCSE - are having the effect ministers wanted to see.
In June, the government said all pupils who start secondary school in England this September will have to take the EBacc subjects when they sit their GCSEs in 2020.
The rise in popularity of traditional subjects may also be linked to academically competitive universities urging students to avoid subjects they perceive to be less rigorous.
In 2011, the Russell Group of research intensive universities published guidance advising students to study traditional subjects at A-level and to take at least two choices from a list of "facilitating subjects" such as English and maths.
Ms Stacey said traditional subjects were seen to be "very good currency" for university.
"We know that they are seen to be very good currency for some universities," she said.
" If your aspirations are to study some subjects at universities where there is a great deal of competition for places, we know that maths is sometimes an absolute requirement for some places, and also is extremely well regarded.
"It's not surprising that some students with those sort of ambitions will focus on that."
The Russell Group welcomed the figures, saying they were "welcome news", but said more needed to be done to ensure bright students from disadvantaged backgrounds got places at top institutions.
Ms Stacey added that the marking of exam papers was "on track" for this year, in contrast to this time 12 months ago when the regulator had concerns about marking progress for the board OCR.
This was "particularly pleasing", she said, given that exams this year were less modular than in previous years and were, therefore, being marked in a relatively small window.
The data was released by Ofqual as A-level candidates wait to receive their results on Thursday 13 August and GCSE candidates the following week.
Students in Wales and Northern Ireland will receive their results at the same time as their counterparts in England, while those in Scotland received the results of their National 4s and 5s, Highers and Advanced Highers on Tuesday 4 August.