Thousands of parents have threatened to take their children out of school for a day in an unprecedented "children's strike" over controversial SATs tests.
The boycott, organised by the Let The Kids Be Kids campaign, is due to take place on Tuesday.
It has been signed by nearly 40,000 people.
It hopes to marshal parents of Year 2 children who have had "enough of endless testing, enough of teachers not being trusted to teach" and objects to SATs tests which it says have increased childhood anxiety.
The campaign has proved controversial.
Nick Gibb, schools minister, said: "Children should only ever be taken out of school in exceptional circumstances."
Lucy Powell, Labour's shadow education secretary, also said she would not condone parents taking their children out of school, but she told ITV News she understood "the concerns that parents have ... with the chaos and confusion that surrounds this year's SATs tests."
SATs are taken by children aged six or seven in Year Two, again in Year Six, aged 10 or 11, and again in Year Nine when the children are 13 or 14.