East Midlands 'joint bottom' of GCSE achievement table
Schools in the East Midlands are "plagued by mediocrity", according to the Ofsted annual report.
The report shows the number of secondary school students achieving five A* to C grades at GCSE in 2014 was the joint lowest in the UK at 53%.
Too few pupils are attending what could be classed as "good" primary or secondary schools, it said.
A spokesman for head teachers said the region faces "challenges" but also has "great heads and teachers".
Ofsted East Midlands director Christopher Russell said: "Education provision in the East Midlands is plagued by mediocrity.
"School quality in the region is well below the English average, and 158,000 pupils attend schools that need to improve.
"Only one council area, Lincolnshire, is in the top third of English local authorities for the proportion of pupils attending secondary schools that are good or better.
Brian Lightman, general secretary of the Association of School and College Leaders, said: "It is unhelpful to make sweeping statements about the East Midlands.
"Leicester, Leicestershire, Derby, and Nottinghamshire are all above the national average in terms of the number of good and outstanding secondary schools."
The report showed 71% of secondary schools were good or outstanding nationally, with Leicester at 88%, Derby at 86%, Nottinghamshire at 81% and Leicestershire at 73%.
"While we know there remains room for improvement, we must recognise the journey that secondary schools have been on," Mr Lightman said.
Mr Russell added: "There are schools and colleges (in the East Midlands) which are equipping children and young people with the education and skills which will serve them well in the future.
"They have strong leaders and high quality teaching, and they show that it can be done. "