Updated

The American Civil Liberties Union intends to sue a Denver-area charter school for allegedly getting rid of a teacher who pumped breast milk on the job.

The ACLU of Colorado filed a "notice of claim" Monday against the Rocky Mountain Academy of Evergreen, a precursor to filing a lawsuit against a government agency. It alleges the school failed to renew the contract of Heather Burgbacher in February because of her pumping schedule.

Burgbacher claims she arranged to have her students do supervised desk work during her 20-minute pumping breaks three times a week.

The school referred questions to the Jefferson County school district. District spokeswoman Lynn Setzer said Burgbacher was a technology teacher who worked under a yearly contract. Setzer said Burgbacher wasn't retained because her position was transformed into a technology adviser to staffers and the school didn't think Burgbacher was a good fit for the new role.

Setzer said Burgbacher was offered an accommodation to fit her breastfeeding schedule and said Burgbacher indicated she was satisfied with that.

Under a law passed in 2008, Colorado employers are required to make reasonable accommodations to allow mothers to pump milk at work.

In the notice of claim, Burgbacher says the school's human resource manager told her the school couldn't accommodate the pumping breaks three times a week and advised her to spend her Thanksgiving break rearranging her breastfeeding schedule and consider switching to formula.

ACLU spokeswoman Rosemary Harris Lytle said the school has up to 90 days to respond to the claim. Unless the school decides to negotiate a settlement, the ACLU will file a lawsuit after the school responds.