HELENA, Mont. (AP) — Montana public school students who have not received a chicken pox vaccination by Oct. 1 will not be allowed to attend school unless they receive an exemption.

A new law that takes effect in two weeks also requires the whooping cough vaccination for pre-kindergarten through high school students.

Children over age 6 were previously exempt from pertussis immunization. Students in grades 7-12 will now need a booster shot called Tdap.

K-12 students who have not received a second chicken pox shot by Oct. 1 must fill out a conditional attendance form.

Medical and religious exemptions must be submitted in writing to the school. Students who already have had chicken pox are also exempt.

Montana this year became the last state in the nation to require the chicken pox vaccination.