Labour has pledged to cap primary school class sizes should it win the general election.
The party has promised to recruit nearly 20,000 more teachers while ensuring around 25,000 currently unqualified staff are full trained within Labour's first term.
Speaking on Thursday, Jeremy Corbyn said: "We cannot go on with so many children being taught by unqualified teachers, it's not right."
He explained the plans are "costed" in the party's manifesto.
Asked about timescales to train new teachers, Mr Corbyn said: "It can be done in the timeframe but obviously you've got to start straight away."
He said Labour would axe tuition fees "which will help to get students into university" to start pursuing a teaching qualification.
Labour has also promised a £7bn fund for school buildings to help repair buildings and install new safety measures such as sprinklers.
It would also fund more time for lesson planning and professional development for teachers, the party added.
Shadow education secretary Angela Rayner said Labour would "close the gap in funding" for pupils with special educational needs and disabilities.
She added Labour would reverse cuts to the pupil premium and boost spending on it above inflation to support the most disadvantaged pupils.
What are Labour's proposed education reforms?
Cap primary school class sizes to 30
Recruit nearly 20,000 more teachers
Ensure 25,000 currently unqualified staff are full trained within Labour's first term
£7bn fund to refurbish school buildings and safety measures
The Institute for Fiscal Studies (IFS) economic think tank has previously said that Labour’s proposals would mean a 15% (14.6%) real-terms increase in per pupil funding over the next three years.
Ms Rayner said: "We will invest in record per pupil funding, restore the pupil premium and close the gap in support for children with special educational needs and disabilities, to give every child the support they need.
“The Tories cannot be trusted to do this. They have slashed school funding for the first time in a generation, leaving pupils taught by unqualified teachers, crammed into super-sized classes, and not receiving the support they need."
General secretary of the NAHT (National Association of Head Teachers) Paul Whiteman said school budgets “are at breaking point”.
While he welcomed the investment promised by Labour, he added more must be done to increase teacher numbers in order to keep up with the number of pupils.
Mr Whiteman said: "Labour’s additional £7 billion to tackle repairs is very welcome and is equivalent to National Audit Office’s estimate of what it would cost to return all school buildings to satisfactory or better condition.
“However, on recruitment, Labour are well short of the 47,000 secondary teachers and 8,000 primary teachers that are needed by 2024 in order to keep pace with growing pupil numbers.
“We need significantly more recruits than Labour are suggesting just to meet rising demand, never mind reduce current class sizes.
Nick Gibb, the Conservative schools minister, said: "Just this week, the Pisa assessment (Programme for International Student Assessment) has shown England’s schools have risen up international league tables under the Conservatives.
“Sadly, in Labour-run Wales, schools ranked worst in the UK and, under the SNP, Scotland recorded its worst-ever performance in reading and maths.
“Conservative education reforms are improving standards in our schools, meaning children can get a better start in life."
Liberal Democrat education spokeswoman Layla Moran said: “While Labour have attempted to copy the Liberal Democrat policy to employ 20,000 more teachers, they have no hope of meeting this target."