"I have very strong feelings of attachment to the school - I didn't want to do anything to harm it and that resistance would take the focus away from the good things that need to continue to happen at the school."
Mr Guy said teachers and principals had worked hard to stop the introduction of national standards after the idea was raised by the National Party in 2007.
Under the system, year levels will have standard benchmarks in literacy and numeracy.
Throughout the year, parents will be informed as to whether or not their child was achieving at that level.
Mr Guy said many teachers and principals were against that idea, as children - particularly young children - learned differently and also at different rates.
He said the negative outweighed the positive and findings made by a number of principals found that the system would not bring any big benefits.
"They're described by the ministry in terms of the children should or are expected to reach certain levels.
"For individual children, that may or may not be appropriate. If a kid's doing really well, then that standard's not going to help them and the standard for a kid who's struggling, it's not an appropriate goal - in either of those cases."
Mr Guy said he felt that the system was not a reliable measuring tool and, in time, would fail.
"Eventually the standards, I believe, will be removed from our system. Sadly, that could take a number of years.
"As a grandparent of preschoolers, I'm really concerned."
Education Minister Hekia Parata was not available to speak to the Herald yesterday.
However in a statement she said: "If Mr Guy feels he is unable to require the teachers under his authority and 'leadership' to implement Government policy, then he has made the right decision to step aside and leave the position to a committed professional leader who is able to work with teachers."
NZ Principals' Federation president Paul Drummond said Mr Guy's resignation showed the conflict that many schools and teachers were going through at the moment.
