Almost half the schools inspected in England last term improved their overall rating, the chief inspector of schools, Sir Michael Wilshaw, has said.
Almost 977 out of more than 2,000 schools checked between October and December had improved compared with their previous inspection.
The proportion of all schools judged to be good or outstanding overall had risen to 74% by the end of December.
Sir Michael said the news was "very encouraging".
He said changes to Ofsted's inspection regime - and the scrapping of the "satisfactory" rating - had driven standards up.
Since September last year, a new rating of "requires improvement" has replaced the "satisfactory" grade.
'Sense of urgency'
Schools falling in to that category are given a set time in which to improve or face intervention and being turned in to an academy.
Schools classed as "outstanding" no longer require regular inspections, which now focus on schools that need improvement.
Sir Michael said while some of the improvement registered in the statistics was likely to be due to the sample of schools checked during the last quarter of 2012, Ofsted's new framework was having a "galvanising effect" on the schools system.
"I'm clear that scrapping the satisfactory judgement and replacing it with 'requires improvement' is injecting a sense of urgency in both schools and local authorities," he said.
"Heads and governing boards now have a much greater focus on tackling the central issues of school improvement.
"This is encouraging and I congratulate all those head teachers who are successfully leading the drive to get their school to 'good'."
However, Ofsted says some of the improvement will be down to the particular group of schools checked last term and it "does not necessarily expect this to be a permanent change in the longer term trend".
Of the 2,102 state-funded schools in England inspected in the last quarter of last year, 9% (185) were judged outstanding overall; 55% were judged good; 31% were said to need improvement and 6% (125) were judged to be "inadequate".
The details are in quarterly statistics published on Thursday.
Christine Blower, the general secretary of the National Union of Teachers said: "At last some positive words from Sir Michael Wilshaw who has described as 'very encouraging' the fact that three quarters of all schools are good, or outstanding. The NUT says congratulations to them all".
But she added: "Many schools will have been working under considerable pressure and stress to improve their inspection rating and this may have been at the expense of working in a way that really is in the interest of all children."