Ontario's education ministry is recommending school boards freeze hiring as it consults on class sizes and hiring practices.

Deputy minister Nancy Naylor sent boards a memo Thursday noting that the government implemented a hiring freeze in June and that school boards may wish to institute similar measures.

When that public service hiring freeze was instituted, the government said it didn't apply to front-line staff such as police and fire services, and Premier Doug Ford said it also didn't apply to nurses or teachers.

Naylor advises the boards to defer filling vacancies for retirements and other leaves for teachers and other staff until the minister gives them an update on the consultations by March 15.

The consultations launched in January contemplate the possibility of removing class size caps for kindergarten and primary grades.

Naylor's memo says the ministry knows school boards are already preparing for the 2019-20 school year, and recommends they "exercise prudence in making hiring decisions" ahead of the upcoming provincial budget.