Schools could be required to give detailed reports to parents on their performance from this summer.
The reports, which were widely piloted last year, will give anonymous marks for pupils in Welsh, English, maths and science at key stages 1-3, based on the teachers' assessments. The school's progress will be given in comparison to the local authority and Wales averages.
The information, depicted in graphs, will also give parents a clearer indication of how their child's school compares to others with similar characteristics, such as comparable free school meal entitlement. This will give a better indication of teaching standards by comparing performance at schools with similar socio-economic backgrounds, rather than contrasting with schools whose pupils are from more privileged backgrounds and catchment areas.
Making this information public is down to individual schools, but the Assembly government plans to consult this term on changes to regulations that will make such reporting statutory.
This week, the Assembly government moved quickly to dispel fears from some quarters that the reports were a return to old-style league tables. A spokesman said the current system of reporting school performance was not good enough, and the new reports were simply a better way of engaging with parents and keeping them better informed.
"These reports are designed to aid schools with their validation, target setting and reporting," said the spokesman. "They allow for a more meaningful contextual analysis of data.
"In no way do they compile any kind of ranking of school attainment in Wales."
Wales scrapped secondary league tables in 2001 and never published primary league tables.
Plans for the compulsory school performance reports are contained in a review of the parenting action plan that was effective until March last year by the Assembly's children and young person's committee.
The reports are intended to bring parents on side by raising the profile of parenting within the general policy of schools. There are also plans to engage parents with a revised admissions policy, making the appeal process easier.
Rex Philips, regional organiser of the NASUWT, said parents and teachers could be forgiven for viewing the performance reports as the forerunner to league tables.
Other unions welcome them. Gareth Jones, secretary of the Association of School and College Leaders Cymru, said: "I don't think it's a league table approach; it's to simplify the whole process and give a more informative set of data."
Philip Dixon, director of the Association of Teachers and Lecturers Cymru, said: "I think the Assembly government wants to give parents more and better information about schools, and it's going to be couched in fairly positive terms. Certainly they have no desire to return to league tables."
The secondary school tables were widely unpopular in Wales with teachers and parents alike, and deemed unfair, divisive and demoralising, as they made simplistic comparisons between schools and failed to take into account socio-economic factors.
An Assembly spokesman said it is still the government's view that league tables are not the most effective way of presenting school performance information.