(CNN)Three Connecticut high school girls, represented by their mothers, have filed a lawsuit over a policy which allows transgender athletes to participate in sports based on their gender identity.
3 Connecticut high school girls are suing over a policy that allows trans athletes to compete in girls' sports
Selina Soule, Chelsea Mitchell, Alanna Smith and their mothers claim in their lawsuit the Connecticut Interscholastic Athletic Conference's (CIAC) policy is a violation of the Title IX act -- which bars discrimination on the basis of sex.
The policy, they say in the suit, results in "boys displacing girls in competitive track events in Connecticut."
CIAC said in a statement after the lawsuit that the policy was implemented in 2013 and is compliant with both state and federal law.
In a statement earlier this week, the American Civil Liberties Union said it would seek to join the lawsuit to defend the interests of transgender student athletes.
"Efforts to undermine Title IX by claiming it doesn't apply to a subset of girls will ultimately hurt all students and compromise the work of ending the long legacy of sex discrimination in sports," Chase Strangio with the ACLU said in a statement.
CNN reached out to five Connecticut boards of education named as defendants in the lawsuit.
James Thompson, the superintendent of Bloomfield Public Schools said in a statement the school system "adheres to Connecticut Interscholastic Athletic Conference guidelines that allow transgender high school athletes to compete in CIAC athletic programs without restrictions -- and consistent with their gender identity."
Glastonbury Public Schools Board of Education did not comment.
The Alliance Defending Freedom (ADF), the conservative nonprofit that is representing the plaintiffs, said in a statement CIAC's policy "robs female athletes of opportunities because of the physical advantages of males."
"Girls deserve to compete on a level playing field," ADF attorney Christiana Holcomb said in a statement. "Forcing them to compete against boys isn't fair, shatters their dreams, and destroys their athletic opportunities."
CNN has reached out to Holcomb for further comment.
As examples, the lawsuit mentions two transgender athletes by name, Terry Miller and Andraya Yearwood, who it says began competing in the 2017 track season and brought home "15 women's state championship titles."
"The more we are told that we don't belong and should be ashamed of who we are, the fewer opportunities we have to participate in sports at all," Miller said in a statement posted on the ACLU website.