The National Union of Teachers has signed the open letter opposing the plan, alongside Early Education, TACTYC, the Save Childhood Movement, and Professor Cathy Nutbrown, among others.
The campaigners want an urgent re-think on the issue from ministers and all other political parties.
The check is being introduced as a schools’ accountability measure to provide a score for each pupil at the start of Reception.
The NUT is set to debate the issue at its Easter conference.
The letter’s signatories are ‘deeply concerned’ about the check, which will be taken by four-year-olds starting in their first six weeks of Reception.
The experts claim the baseline is ‘unreliable, disruptive, statistically invalid and harmful to child well-being’.
They are also against the move to make the EYFS Profile optional from September 2016, which they say is ‘a rounded assessment of children’s development based on observation over time’.
Campaigners also point out that baseline assessment was introduced by the Labour Government in 1997 but withdrawn in 2002 because it proved unworkable.
The letter is the latest sign of mounting opposition to the baseline, which will be piloted from September.
Schools that want to take part from September must choose one of six commercial providers of the baseline by next month.
Campaigners say that although it is not statutory for schools to use the check, heads will feel under pressure to sign up to a baseline scheme to protect them from punitive measures should their school not reach the Government’s floor standards when children reach Key Stage 2.
The letter’s signatories also include the National Day Nurseries Association, the Pre-school Learning Alliance and PACEY.
- Read the open letter here