Principals are asking parents to sign statutory declarations to ensure families are not gaming strict enrolment policies as public schools in Sydney continue to struggle with overcrowding.

High achieving schools and those in popular areas have especially rigorous enrolment requirements, insisting that tenancy agreements stretch for at least the first six months of the year to stop families leasing a property simply to gain enrolment.

Overcrowding is a worsening problem for Sydney schools and the NSW Department of Education has changed the boundaries for 11 schools this year in a bid to ease the pressure in areas with ballooning populations.