Secondary school children will be asked to keep a distance of 2 metres where possible.
New social distancing guidelines have thrown the full re-opening of schools in August into doubt.
According to Department of Education guidance, primary aged children from 3rd to 6th class will be asked to keep one metre apart.
For children up to third class, social distancing won't be required.
While secondary school children will be asked to keep a distance of 2 metres where possible.
The ASTI is concerned that social distancing rules mean not all secondary school students will be returning everyday from September.
The union says it won't be possible in schools with up to 1,600 students.
General Secretary Kieran Christie believes they will probably have to keep a mix of in-class and remote lessons:
''They're from 12 to some of them over 18 indeed (the students), you can't put 30 people like that into a classroom with a teacher'', he said.
''And some of the smaller classrooms we have in particular would be an impossibility even in the standard sized classroom''.
The key points of the document include:
• The measures outlined in this guidance are aimed at risk minimisation of COVID-19, for young people, teachers, other staff, their families and the wider surrounding community, recognising the importance of education for health and wellbeing.
• No person (child, teacher or parent) should attend an educational setting if unwell or any members of their household are unwell with symptoms consistent with COVID-19.
• Social (Physical) distancing, hand hygiene and good respiratory etiquette should be observed by all (children, teachers, parents and visitors).
• This guidance should be read in conjunction with the Government Roadmap for the reopening of society to correspond with national policy.
You can read the entire document here.