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DENVER — Some Colorado school districts are cracking down on parents of students who are not vaccinated.

Colorado has some of the lowest vaccination rates in the country, KDVR reports. Few districts enforce the law, but that’s changing.

School districts want to keep a record of student vaccinations in case there is an outbreak so the can determine who is at the greatest risk.

The Boulder Valley School District has the highest number of children in the state out of compliance with the law, about 1,100 to date.

The district is giving parents until Dec. 2 to comply. They have to supply a current certificate of vaccination or a statement of exemption.

Littleton Public Schools is also taking action.

Students without vaccinations were told to stay home starting Friday.

Brighton School District 27J also keeps non-vaccinated students out of classrooms.

Gov. Jared Polis is asking for another $2.5 million in next year’s state budget for the health department. That money would go to increasing the vaccination rates.