The Education Policy Institute says the new prime minister should target the issue with "laser-like focus".
Related stories
GCSE results, resits and appeals - what to do if you are unhappy with your grades
Are the UK's top universities really 'hoovering up' students?
U of Michigan Attempts to Disrupt the Transactional System
The Small Section Cut Session
Michigan Narrows Gap in Who Can Get Free Community College Tuition
Accreditor Puts Lane Community College on Warning