However, this timeframe had been labelled "not ideal" by a Dunedin principal among those who signed the letter.
Otago Secondary School Principals’ Association president and Otago Boys’ High School rector Richard Hall said schools needed a decision as soon as possible.
"It absolutely needs to be some concrete, workable and manageable solution given the fact that for the majority of students their year will be three-quarters over by then."
Ministry of Education curriculum centre leader Ellen MacGregor-Reid told the Otago Daily Times yesterday a decision about NCEA assessments would be made over the coming weeks.
"We expect to be able to make a decision no later than September and will keep schools and kura updated as things progress,” she said.
Sent by leaders of 10 regional principals' associations last week, the letter said unprecedented disruption had been caused by the Covid-19 pandemic this year.
"If we aren't already at it, out sector is very close to breaking point."
The disruption caused by staff and pupil absences affected all pupils, especially the most vulnerable, who were at risk of disengaging from education completely, the letter said.
"Now is the time to provide certainty in what support will be available for our students studying NCEA."
Isolation periods for staff and pupils with Covid-19 were often prolonged because they lived with others who would subsequently test positive, Mr Hall said.
Otago Boys’ High School had already surpassed 1000 hours of teaching by a relief teacher this year.
"That’s a huge amount."
"It’s been a real challenge for these boys. They loose their continuity."
The Ministry of Education sent a letter to schools on Monday stating the situation was being looked at.
"This is a high priority for the ministry and NZQA and we will be in touch again as soon as possible," it said.
Otago Boys’ High School pupil Sam Gavin (17) said the situation differed from lockdowns, in which pupils had online learning set everyday.
"When you get sick with Covid or something for the week, you might actually be quite sick, so you can’t even do anything."
Fellow pupil Isaac Ottrey (17) said last term was "very disrupted" by absences as pupils and teachers fell ill.
"Towards the back end of last term, there was definitely a lack of motivation.
"Boys were getting very lethargic and fatigued just coming to school and having so much to catch up on and so much ahead of you still."
