Britain's top teachers are unhappy with their students' grades, but it's the government they're blaming.

Results for British high school test exams have fallen for the first time in 24 years, prompting some educators to accuse the government of arbitrarily toughening standards in a bid to curb grade inflation.

The fall in tests for science, English, and other subjects has also has drawn angst from children and parents, who have voiced fears that students have been penalized to make a political statement.

Education Secretary Michael Gove has denied leaning on evaluators to give high school students a tough time, but some principals are demanding that tests be re-graded.

One teachers' association has threatened to sue over the issue, and Britain's education regulator has promised an investigation.