School computer networks blocked more than 2000 online threats every minute when students returned to school after the first Covid-19 lockdown last year.
The schools' Government-funded Network for Learning (N4L) says it blocked 120 million cyber security threats to schools during term two last year, 14 per cent more than in term one.
They included a spike in "distributed denial of service" attacks, where a flood of internet traffic attempts to overwhelm a website, in the week of May 24 shortly after schools reopened for all students after the national lockdown.
The numbers are massive because of many automated systems which attempt to update repeatedly, but include a small minority of cases where students tried to access material such as games and pornography which are blocked by the network.
Blocks of gaming sites doubled in primary schools between the first and second terms, and rose by 24 per cent in secondary schools, rising to 20 per cent of all blocks made by the network - second only to blocks of file-sharing and storage sites, which made up 21 per cent of all blocks.
Porn sites represented only 1.4 per cent of all website blocks. They increased by 42 per cent in primary schools but fell by the same percentage in secondary schools which account for the vast bulk of attempted porn access.
N4L chief executive Larrie Moore said schools were the largest consumers of daytime internet in the country and were not immune to online threats.
"Schools are increasingly reliant on safe internet for teaching and learning and we are doing more to keep them safe and secure while at school and beyond," he said.
"It is a massive task involving many organisations and our role is expanding. Technology is an important part of the online safety solution but it is never bulletproof. Ongoing vigilance and education is paramount.
"This year we are building our security operations capabilities, providing greater cyber security support to schools and continuing a four-year Ministry of Education programme to upgrade the wireless networks inside schools."
The company's update report said that the country's 800,000 school students and 55,000 teachers used 174 terabytes of data during the second term, the equivalent of six and a half years of streaming Netflix-quality video.
Streaming media account for 25 per cent of all data consumed.
However, neither Netflix nor YouTube figure in the top 10 websites measured by the amount of time spent on them - a list dominated by Google with just over 60 per cent of all time spent on the web in primary schools and about 43 per cent of web time in secondary schools.
Facebook ranked fourth in primary schools and fifth in secondary schools, but accounting for less than 2 per cent of web time in both sectors.
Surprisingly, data consumption per student was lower in Auckland, at 10.7 gigabytes in term two, than in all other regions except Northland, Tasman and Marlborough.
The highest data use per student was on the West Coast (24.3 gigabytes), followed well behind by Manawatū-Whanganui (16.5 GB) and Nelson (16 GB).