Police learned of the fights when someone gave a cell phone containing videos of the brawls at the Corpus Christi State School to an off-duty officer on Friday, police Capt. Tim Wilson said by phone from Corpus Christi.
"Workers were running their own fight club using clients. It's pretty appalling that someone would think of this," he said.
In the videos, which show several fights dating back to 2007, mentally disabled male residents can be seen fighting each other while the employees watch. In one video, a disabled resident raises his hands in victory after a bout, Wilson said.
"It's pretty appalling. I've been in police work over 30 years and I've never seen anything like this," he said. "These people who were charged with caring for these clients were exploiting them for entertainment."
Police expect to file charges later this week, said Wilson. Most of the employees seen in the videos have been identified, he said.
Laura Albrecht, a spokeswoman for the Texas Department of Aging and Disability Services, which oversees the institutions known as state schools, said the videos show seven current and four former employees. The current employees have been placed on emergency leave pending the investigation.
"Any abuse or neglect of residents placed in our care will not be tolerated," said Albrecht.
In addition to Corpus Christi police, the abuse allegations are also being investigated by Texas Adult Protective Services, the Health and Human Services' office of inspector general, and the Nueces County District Attorney, Wilson said.
These are the latest in a spate of abuse allegations against state school employees in recent years.
A 2008 federal report cited negligent and abusive care that violated residents' rights. It cited 53 deaths linked to preventable conditions at the institutions.
The report also called hundreds of reports of abuse and injuries to patients "disturbingly high" and said more than half of state facilities are in danger of losing Medicaid funding because of care and safety problems.
The state Legislature is considering measures to tighten standards at the institutions, including requiring fingerprinting, background checks and random drug testing of all employees. Lawmakers also want to create an independent ombudsman to investigate injuries and deaths and oversee an abuse-and-neglect telephone hot line.