Parents supporting the Let Our Kids Be Kids campaign have kept children out of school.
More than 40,000 parents have signed a petition calling for primary school tests, which are due to be taken later this month, to be scrapped.
The number of children kept at home today (3 May) is still unsure.
A social media campaign has been urging parents to take children on educational activities for the day.
The campaign organisers say children are "over-tested, over-worked and in a school system that places more importance on test results and league tables than children's happiness and joy of learning."
Ofsted has shared findings from pilot inspections carried out in 115 schools this autumn, ahead of the full rollout of its renewed inspection framework.
The TV, radio and multi media campaign deals with the root causes of absences and identifies ways to approach conversations about wellbeing that can help pupils to improve their attendance.
The government will publish a new set of enrichment benchmarks, with schools asked to ensure every child has access to activities across five categories of enrichment.
The policy introduces the new Chief Regulator’s Rebuke - a new tool which can be used when an awarding organisation is found to have breached rules, but not in a way that warrants a financial penalty.