The school has a large roll, at 605, and the school hall was being used as a classroom this year.
The first of the two new classrooms was due to open in Term 2, however, delays pushed the opening back until yesterday.
"We've had the school hall out of action for nearly a year.
"It's impacted on us not being able to have assembly on wet days."
Other classes were being held in the former library so having the new classrooms will give students the space to learn in more appropriate environments, he said.
The roll looks like it will end the year on about 625 but numbers should slowly decrease in the next few years due to year sizes being capped at about 80.
"We've got big years in Year 3 and 4 with about 100 children, as those students go through the roll will naturally decrease."
However, if new housing developments in Havelock North went ahead as planned in the next few years, numbers would increase at all schools in the area, he said.
"We just don't want to keep getting bigger and bigger."
A new school, which had been discussed by community members earlier this year, would ease the pressure and make for a nice roll size at each of the existing schools, Mr Reed said.
Te Mata School principal Michael Bain said work on his school's two new classrooms was going to start in November and would hopefully be finished by the beginning of next year.
The school roll is expected to be 625 at the end of the year.
The new classrooms will bring capacity up from 650 to 700, which will ease pressure on future roll growth which is expected with new housing developments, he said.
"We will be well positioned with those two new classrooms."
To keep class sizes down the school has one class in the AV suite and another in the music suite, so having the new classrooms will mean these spaces can be used as intended again, Mr Bain said.
Lucknow School principal Paul Grundy said his school roll had started lower than usual at about 250 at the beginning of the year but it had slowly increased to 285 children and they would be ending the year with about 300.
They had the capacity for 320 and with two new classrooms due to open at the beginning of next year it would bring capacity up to 375.
"They're not required at present but the decision has been made to put them here for future growth."
A site at the former Arataki Camping Ground was earmarked for a new school by the Ministry of Education, however, it was then deemed unsuitable for educational purposes due to the odour from the Te Mata Mushroom farm.