A Belfast primary school principal is calling on the Education Minister to clearly state that teachers will not be asked to project transfer test grades if a second coronavirus wave makes the exam impossible.
St John the Baptist headmaster Chris Donnelly said it would be "unacceptable to ask a teacher to make a call as to whether a child gets into a grammar school or not".
This year's post-primary transfer tests are being held two weeks later than usual due to the coronavirus pandemic.
The AQE and GL exams are set to run over four Saturdays from November 21 to December 12. But a second wave of Covid-19 in the autumn could disrupt these plans.
Mr Donnelly said: "If we ended up in a second lockdown, I don't see how grammar schools could use academic selection to choose pupils for the following year.
"Teachers have been asked to predict grades for cancelled GCSE and A-level exams but it would be disastrous to do this for the transfer test. So much rests on the grade awarded.
"It would be unacceptable to ask a teacher to make a call as to whether a child gets into a grammar school or not. It would put immense pressure on teachers. It would poison our relationships with pupils and parents, and it would open the door to litigation.
"Peter Weir needs to make a clear statement reassuring primary school teachers that we will not be asked to project grades."
Last year more than 8,000 pupils sat transfer tests which are used by the vast majority of grammar schools here to select pupils.
Northern Ireland Commissioner for Children and Young People Koulla Yiasouma and head of the Catholic Church in Ireland Archbishop Eamon Martin have called for the exams not to go ahead this year.
But their appeals are likely to be ignored despite P6 pupils having missed so much of the school year due to the coronavirus crisis.
The Education Minister last week announced a phased return to school here from late August.
He said the reopening would be subject to safety and medical guidance.
But Mr Donnelly urged the minister to detail the social distancing measures that would apply so that schools could start making preparations now.
"We need to know if we will be adhering to the existing social distancing rule of two metres in Northern Ireland, or whether it will be reduced to the World Health Organisation's one metre guideline," he said.
"That's crucial so we can make plans as to how to divide classes. Without that knowledge, we won't know how many kids we can actually have in each classroom.
"In England there has been talk of around 15 children in a classroom. I don't know how you adhere to social distancing with so many in a class."
The west Belfast principal added: "We need clear guidance from the minister as soon as possible so we can decide if it's necessary to split our classes of up to 30 children into three, four or even five groups. We must be told this by next month at the latest so we can map out the way ahead."
Mr Donnelly said that as smaller classes were necessary, children would not be returning to school full-time.
He added: "We need to know if the department will allow schools themselves flexibility in drawing up timetables or if the minister will direct the approach taken. And what approach will that be?
"Will Peter Weir propose splitting groups into morning and afternoon sessions or will he want children to be in school for a full day but perhaps only two days a week?"
Mr Donnelly also urged the Education Minister to send unemployed substitute teachers into our most deprived areas to help children during the pandemic.
The Executive last week announced a £12m fund to assist substitute teachers during the Covid-19 crisis. They are now being paid without being required to work.
Mr Donnelly suggested that they could be deployed in deprived areas.
"There is widespread concern that our poorest and most vulnerable kids are destined to be the most disadvantaged as a consequence of the pandemic," he said.
"It would be an innovative step for Peter Weir to use this pool of teachers to help counter the adverse impact of the enforced school closures by allocating them to schools in communities with the greatest social and economic deprivation.
"It would be a way of targeting work on numeracy and literacy and also offering pastoral support to those kids who need it most."
In response to the issues raised by Mr Donnelly, the Department of Education said that a "very wide range of issues" were under consideration.
The department would be "working closely with the whole education sector, including school principals, to develop appropriate guidance to assist schools with planning provision", it said.