The Principal’s Federation wants some parts of the school system to be immune from political interference.
That call would be a lot more powerful if the Federation was dedicated to improving professional and educational standards rather than being more like a union that appears to be at least as interested in members’ pay, conditions and other employment and political issues.
They could take the lead from the medical workforce. The Association of Salaried Medical Specialists deals with employment issues and leaves professional matters to professional bodies like, for example, the College of GPs.
Principals and teachers would have far more standing if they took a more professional approach with a clear division between the organisations which deal with employment issues and those which deal with professional matters.

This would be the same Principals’ Federation which:
* passed a vote of co confidence against Anne Tolley in April 2011
http://www.nzherald.co.nz/education/news/article.cfm?c_id=35&objectid=10718319
* has a past-president who is now a Labour candidate this election, and who posts offensive comments about the education minister on social media
http://whaleoil.gotcha.co.nz/index.php/2011/08/meet-pat-newman-part-one/
Pot; meet kettle. For the Principals; Federation to be calling for the de-politicisation of education is hypocrisy on a grand scale.