The union's resolved a dispute with the Department of Education over legal protection for teachers.
The calculated grades system for this year's Leaving Cert has been in doubt since last night, when the ASTI said it wouldn't engage with the model.
They had concerns the state indemnity being offered didn't go far enough - and wanted a guarantee that if a student took a claim, 100 per cent of the legal costs would be covered.
A meeting has been taking place between union and department officials this afternoon - and the ASTI now says it's secured the necessary clarifications.
It's been assured that if a student unhappy with their grade sues, no teacher will have to employ their own legal team to defend themselves and run the risk of racking up large expenses.
The ASTI says it's now in a position to advise members to engage with the calculated grades system for this year's Leaving Cert