Schools preparing to receive their GCSE results today have been told to expect "variable" grades.
There are particular concerns among some headteachers about English and maths grades, according to initial reports.
The potentially unpredictable results are said to be due to significant alterations to the qualifications this year.
Brian Lightman, general secretary of the Association of School and College Leaders, which represents a large proportion of secondary heads, said: "We are getting some individual reports of volatility, but we don't know about overall trends yet.
"Some schools have seen surprises. Some schools have seen results which are lower than expected."
More top news
The study reveals cases of slave driving and human trafficking suffering delays, being prematurely shelved or being overlooked entirely.
David Clarke was arrested after a four-hour standoff in which two members of staff were taken hostage. Both escaped unharmed.
New York's attorney general launched the civil rights investigation after dozens of women accused Harvey Weinstein of sexual harassment.