GCSE results: Students in for a shock?
21 August 2013 Last updated at 09:21 BST
Students will receive their GCSE results on Thursday where the results are expected to be more unpredictable than usual.
Examiners have been told to tighten up the marking of maths and English papers while regulators have said that science GCSEs are more challenging.
The BBC's education correspondent Gillian Hargreaves reports.
First broadcast on BBC Radio 4's Today programme on Wednesday 21 August 2013.