In a letter to parents and carers, Curtin Primary School principal Merryn O'Dea said a licenced assessor found six areas that needed lead paint remediation work.

One of these areas tested, an external door sill in the junior courtyard, returned a reading of 0.93 milligrams per square metre (mg/sq m).

This is more than double the acceptable threshold for an external surface, which is 0.43mg/sq m.

"This sliding door is not used as an exit and is normally kept closed. On the advice of the assessor, the area within one metre of the door has been blocked off," the letter said.

"This will not impact on the use of the courtyard. No classrooms or learning spaces are impacted."

The courtyard will undergo environmental cleaning over the coming weekend and other areas of the school will be assessed for lead paint.

Parents have been directed to speak to their doctor if they have health concerns.

The Education Directorate issued advice to all ACT public schools after lead paint contamination closed 11 classrooms at Yarralumla Primary School two days into Term 3.

Students were unable to access the affected classrooms for up to six weeks.

Since the start of term, lead dust contamination has been discovered in five rooms at North Ainslie Primary School and in the school hall at Alfred Deakin High School.

Two rooms reopened at North Ainslie Primary School last week and further lead paint assessment will be conducted in the upcoming school holidays.

READ MORE:

An Education Directorate spokesman said the directorate had recently updated its building management policies and communicated this with schools.

"This policy included advice to schools that schools do not engage contractors to do any building or maintenance works in their school without first contacting the Infrastructure and Capital Works team within the directorate," he said.

"This team will work directly with schools to ensure all potential hazards and health and safety risks are addressed prior to the commencement of any school maintenance works."