AUSTIN, Texas — A federal appeals court on Friday dismissed a class action in a lawsuit challenging Texas' foster care system, but sent the case back a lower court to try again.

The lawsuit by New York-based advocacy group Children's Rights claims the Texas foster care system is unconstitutional and forces thousands of children to live in poorly supervised institutions, frequently moving them from one place to another and often splitting up siblings.

The lawsuit was filed in 2011 on behalf of nine Texas children. A state district judge in Corpus Christi allowed the class action, but Friday's ruling by the New Orleans-based 5th U.S. Circuit Court of Appeals said the plaintiffs had not properly established a legal class.

Children's Rights Executive Director Marcia Lowry said the group is confident it can meet the legal standard and will continue to press their case.

"We are not only pursuing it ... we still expect to present our case and get the reforms on behalf of Texas foster children," Lowry said. The group has continued to collect evidence to present to the lower court.

Lowry said the appeals court ruled the class action had bundled too many issues together. Those must be separated and better supported by evidence for each, Lowry said.

The lawsuit contends that "deficiencies" in the system, including overburdened case workers and poorly supervised contract providers, have led to a number of harmful conditions for the 12,000 children in long-term foster care. It cites statistics showing that, as of 2009, children who had been in the state's custody more than three years had been placed in an average of 11 different homes or other settings, such as shelters or residential treatment centers.

Cycling children through the system in this manner doesn't comply with "reasonable professional standards," the complaint alleges.

The lawsuit also is critical of the state's use of foster group homes that accommodate seven to 12 children. Those homes can be "little more than poorly supervised dormitories," and provide further evidence of how the Texas system differs from conventional standards, according to the suit.

Much of the lawsuit's narrative was drawn from media accounts, including an Associated Press story detailing how one foster group home in East Texas was a collection of mobile homes and how the state repeatedly ruled out allegations that young girls living there were sexually abused by their foster father until he was arrested on those charges.

According to statistics compiled by the agency, the number of caseworkers in Child Protective Services has risen from about 2,950 in 2005 to about 4,660 in 2011. The number of adoptions consummated during that time period also increased dramatically, from 2,512 to 4,803.

Patrick Crimins, spokesman for the Department of Family and Protective Services said, "As the Texas agency charged to care for children who have suffered abuse and neglect, we work every day to ensure their safety and well-being. We will continue to dedicate ourselves to that very vital work."