- It expects about 23,000 schools to be affected in the first of its seven planned walkouts.
- Strikes in Scotland continued on Monday, as part of a 16-day programme.
Teachers' strikes in England and Wales are to go ahead, after talks between the government and unions ended without resolution.
The National Education Union (NEU) said the education secretary had "squandered an opportunity" to avoid Wednesday's strike action.
It expects about 23,000 schools to be affected in the first of its seven planned walkouts.
Strikes in Scotland continued on Monday, as part of a 16-day programme.
NEU joint general secretaries Dr Mary Bousted and Kevin Courtney said the government had been "unwilling to seriously engage with the causes of strike action".
They are demanding a "fully funded, above-inflation pay rise for teachers".
National Association of Head Teachers general secretary Paul Whiteman said the meeting had been "unproductive" as the secretary of state "was unable to make any offer on the eve of industrial action".
Further talks were expected, he added.
Earlier this week, Gillian Keegan said she was optimistic that the two sides could find "common ground".
Writing in the Sunday Telegraph, she said she was "disappointed" that Wednesday's walkout was going ahead, but she hoped to continue "constructive discussions" on issues including pay.
She reiterated a call for teachers to inform school heads if they intended to strike, in order to avoid "unnecessary disruption", and to ensure safety for children.
But she acknowledged that teachers had no obligation to do so. The NEU has advised its members to ignore the request.
The government is keen that schools remain open during Wednesday's walkout - although this will ultimately be decided by each headteacher.
More than 100,000 teachers are expected to strike, with industrial action expected on the same day from train drivers, university staff, and civil servants.
Speaking to the Sunday with Laura Kuenssberg programme, Labour's shadow education secretary refused to say whether teachers should go on strike.
Bridget Phillipson criticised ministers for failing to be "serious" in negotiating, citing the "disruption" the strikes would cause so soon after pupils' education was hit by the pandemic.
Although Wednesday's action is limited to England and Wales, walkouts are planned across the whole UK by the NEU and other unions.
Teacher salaries in England fell by an average of 11% in real terms between 2010 and 2022, after taking rising prices into account, says the Institute for Fiscal Studies.
Most state-school teachers in England and Wales received a 5% pay rise in 2022.
In Northern Ireland, many teachers were offered 3.2% for 2021/22 and 2022/23. In Scotland, teachers have rejected both a 5% increase and a more recent offer of up to 6.85%.
Ms Keegan says the government has provided an extra £2bn in school funding, insisting that this meets union demands.