The secondary teachers' union wants more help for schools dealing with increasing numbers of disruptive and dangerous students.
A paper prepared for the PPTA's annual conference calls for more funding, including extra pay for teachers in schools with high numbers of badly-behaved students.
It also recommends that a new index to target staffing to those students be investigated.
But it says that does not involve colleges being secretly classified by the number of such students on their rolls.
Association president Robin Duff says it may be a matter of having anti-social behaviour as one of the measures included in decile ratings which rank schools according to the economic background of their students.
A survey of teaching staff in the Hutt Valley and Wellington on the incidence of bad behaviour is to be released at the annual conference later this month.