Unions are stepping up their campaign to boycott next year's Sats tests – as headteachers launch a petition against the current assessments.
Both the NAHT heads' union and the NUT teaching union have written to their school leadership members outlining plans to carry out an indicative ballot this month.
Meanwhile, a group of headteachers has launched a petition calling for a boycott of next year's Sats. So far, more than 100 senior leaders have added their signatures.
The unions plan to hold indicative ballots in October, in order to provide fair notice to members. If successful, the NAHT says a full ballot will be held in March.
However, the NAHT says it expects the government to make some changes to the current assessment, following union negotations with the Department for Education (DfE).
'Change is likely'
In a letter to heads, Russell Hobby, general secretary of the NAHT, wrote: "We are likely to get a serious proposal for change from the government. The question is whether it will be timely and efficient."
He added: "Despite the discussions, as yet nothing has been agreed. National Executive therefore has asked HQ to continue our preparations for action."
An indicative ballot may be delayed if the DfE does make an anouncement on primary assessment, depending on the government's proposals.
Mr Hobby wrote: "If a proposal arrives from the government before the indicative ballot (something we think is likely), we will seek your views on the proposal first."