Many pupils in years seven, 12 and 14 are back at school on Monday for the first time since March.
Schools closed to all but a few pupils that month due to the coronavirus pandemic.
Education Minister Peter Weir has said that opening schools was probably the "top priority" for the executive.
Speaking on the BBC's Good Morning Ulster programme, he said that the highest level of staff and pupil safety is "obviously the key concern".
Ballyclare Secondary School will not be opening on Monday after a pupil tested positive for Covid-19 after being in the school on Thursday, 20 August.
St Louise's College, also on the Falls Road, also confirmed a positive case of Covid-19 among the school community.
'Bumps along the road'
The education minister said that there will be "undoubtedly bumps along the road" and staff and pupils will have to adapt to a new way of working.
When asked about school closures, he said that "if there is a particular problem in a particular school then that may lead to a particular action".
"Is everything going to be smooth? No. But I think there is a critical need to get our young people back to school, as indeed our young people have highlighted, that there is a much greater need to get our children back into school safely."
Mr Weir said that pupils should adopt safety measures at home.
"What we have seen in terms of international study is that the opening of schools has not led to major problems, but what it does highlight is that problems will not necessarily be in the classroom," he said.
"It is important when a child gets home that they change their clothes, they wash and take precautionary measures."
'Schools left unsupported'
A union representing many principals told a Stormont's committee there is still a "real risk" that many schools will only be able to open part-time.
According to Department of Education (DE) guidance school leaders, for example, must carry out individual risk assessments to assess whether it is safe for some vulnerable staff and pupils to return to school.
The National Association of Head Teachers (NAHT) said that "school leaders have been left unsupported to make serious decisions on risk with potentially very serious ramifications".
Sandra Isherwood, principal at Jones Memorial Primary School in Enniskillen, County Fermanagh, told Good Morning Ulster that staff would be giving parents a tour of the school to allow them to see what safety measures were in place.
Following safety guidance issued to schools last week, Ms Isherwood said principals "were left to sit down and see how each individual classroom would best fit that purpose".
"So a lot of that is based on individual schools, because every school is totally different, and the intake of pupils is totally different," she said.
Guidance for the reopening of schools states that face coverings are "strongly encouraged" in NI schools if social distancing is not possible, but are "not generally recommended for routine use".
A number of schools have already said that they will be encouraging the wearing of face coverings and Belfast Royal Academy is making it mandatory for pupils and staff to wear face coverings when they return.
The guidance for the journey to and from school is that it is "strongly recommended that all pupils, regardless of age, should wear a face covering on all buses, trains or taxis for the journey to school" if it is appropriate in their case.
Schools are also required to keep most pupils in whole-class "bubbles" to limit mixing.
The need for "bubbles" will mean that most pupils should stay in their own class groups for the entire school day and not mix with pupils in other classes.
In many schools there will be measures in place such as:
- Staggered starts and ends to the school day so parents are not dropping all children off at once
- Staggered meal and break times so children are not mixing in the playground with a lot of others at one time
- School meals may have to be eaten in classrooms or even outside
- One-way systems in school corridors
- Children may not be able to bring things like books or stationery home and then back to school
- Items such as Lego and soft toys that are difficult to clean are likely to disappear from classes
Previous 'Education Restart' guidance issued by the department in June had suggested that many pupils may only be able to return to school part-time in September.
Many students starting back at school will have received examination grades last week.
There was a significant rise in the number of top GCSE grades awarded in Northern Ireland, just days after the education minister said they would be solely based on grades provided by schools.
Mr Weir also made a similar decision on A-Level and AS grades which had already been awarded to students.