The Conservatives are promising to strengthen England's education watchdog Ofsted, as they attack Labour and Liberal Democrat plans to replace the current inspection system.
Prime Minister Boris Johnson is announcing plans for longer inspections and an extra £10m funding for Ofsted.
There will also be trials of "no-notice inspections", where schools could be visited without any prior warning.
But Labour and the Lib Dems want to replace Ofsted with different bodies.
Head teachers say the idea of no-notice inspections has been proposed and rejected as impractical so many times before that it is "flogging a dead horse".
The Conservatives are setting out a clear dividing line in their policy on schools - calling for a bigger role for Ofsted while opposition parties are moving in the opposite direction and wanting to close it down.
Mr Johnson says there will be an extra day added to inspections of secondary and large primary schools to focus on behaviour, bullying and extra-curricular activities, such as sport.
He will also announce a pilot of inspections without any notice - an idea previously floated and then rejected because of concerns that inspectors could arrive on days when none of the relevant senior staff was present.
The idea behind "no-notice" inspections had been to reveal the unvarnished reality of schools, rather than giving staff a few hours to prepare.
Paul Whiteman, leader of the National Association of Head Teachers, rejected the idea of no-notice inspections as making "absolutely no sense".
"No-notice inspections will do more harm than good - they will result in more wasted time for inspectors, whilst arrangements are frantically put in place to meet their needs," said Mr Whiteman.
"They will be more disruptive and stressful to teachers and pupils; and will give zero additional insight in return," he said.
Mr Johnson will also confirm plans to end the exemption, introduced by Conservative education ministers, that saw "outstanding" schools not having to face regular inspections.
"Ofsted is an independent and trusted source of information for parents and teachers and their inspections help to raise standards in our schools," said Education Secretary Gavin Williamson.
He said that Labour's plan to scrap Ofsted would leave parents without "reliable information about the performance of their child's school".
Geoff Barton, leader of the ASCL head teachers' union, welcomed what he called a U-turn on removing the exemption on inspecting outstanding schools.
But he said the idea of no-notice inspections had been "raised and rejected" so many times before that there was no "purpose in flogging this dead horse yet again".
'Unfit for purpose'
Labour has argued that Ofsted is "unfit for purpose" and needs to be replaced by a more effective body for checking standards.
It would remove grades for schools - such as outstanding, good or inadequate - and would set up a new organisation to inspect them.
Shadow education secretary Angela Rayner has warned that too often, Ofsted judgments were a reflection of "the affluence of a school's intake and the social class of its pupils - not the performance of the school".
She said the education watchdog had "created a culture of fear among teachers, driven thousands from the profession, and fails to give parents meaningful information about their children's school".
The Liberal Democrats say they would replace Ofsted with a new "HM Inspector of Schools", with inspections every three years.
Under the current arrangements, the Lib Dems say that more than a thousand schools have not been inspected for over a decade.
"Hundreds of thousands of pupils could be in declining schools, but we simply don't know," said the Lib Dem education spokeswoman Layla Moran.
"The Ofsted brand is fundamentally broken. It creates a huge unnecessary workload and stress for both pupils and teachers. It needs to be replaced with a schools watchdog that parents and teachers can trust," she said.
The Public Accounts Committee warned last year that Ofsted had faced a significant cut in the value of its budget - which was £132m in 2018-19.
The MPs warned that the amount spent on inspecting schools had fallen by 52% in real terms between 1999-2000 and 2017-18.