Ministry of Education figures show nearly one in five schools is defying the Government over its national standards in reading, writing and maths.
The ministry has almost finished working its way through 2025 school charters, which this year must include targets based on the standards.
So far it has found 363 that do not include the standards and officials still have another 200 charters to consider.
Opponents of the standards expect many of those documents will swing their way because the schools left it until the last minute to submit their charters.
The spokesperson for the Boards Taking Action Coalition, Perry Rush, expects the total number of schools who have not included the standards will exceed 400.
The number is fewer than the 600 they had hoped for but Mr Perry says the Government should pay attention.
Opponents say the action has been taken by school boards - not by teachers and principals.
And they say the current number of rebel schools is just the tip of the opposition as most schools did not want to break the law by leaving the standards out of their charters altogether.