Parents in the Chester Community Charter School community are furious after the alleged abuse that led to 20 school staff members being criminally charged on Monday.

The Delaware County District Attorney's office says nine staffers at the school were charged with simple assault and other offenses related to "techniques to restrain and punish children," and 11 staffers were charged with at least one count of failing to report the crime of endangering the welfare of a child. Investigators said the abuse dates back to November. 

According to the district attorney and confirmed by a school spokesperson, many of the accused staffers were employees of Peak Performers Staffing, LLC, a company co-founded by Jennifer Woodhouse and Emmanuel Gilbert of Chester. Woodhouse said the Peak Performers staff members were trained in safety care techniques; however, when investigators asked for records of the training in restraints and crisis prevention techniques, it was revealed that none of the staffers had the mandated up-to-date training, District Attorney Jack Stollsteimer said on Monday.  

Chester Community Charter School said that outside companies' employees "were completely unqualified to manage children." A spokesperson for the school said it's cooperating with investigators and has pledged to cut ties with the staffing agency.

Peak Performers' website has since been taken down. CBS News Philadelphia's calls to the company for answers have yet to be returned.

Two parents who didn't want to be identified spoke to CBS News Philadelphia about what happened to their children.

"I got a call maybe the first week of January from Chester Township police stating that it was an incident of assault – two teachers or staff members...and that two of my sons were in this assault," a mother said. "I cried, because my sons are little. They're petite. They're little guys. They're only 7 and 8."

Another mother said, "So what I do now is I just question him every day when he come home. I just question him. He's very scared, though, but I know I just can't leave him home. I gotta send him."

Chester Township police say six people have turned themselves in since the charges were filed, and others are making arrangements to do so. A few more parents have called asking to speak to detectives about incidents that might be related.

"As soon as school administrators learned that there was any possible violation of approved methods, it took swift and decisive action to terminate the contractor," a statement from Chester Community Charter School read in part. "CCCS employees who are alleged to have carried out such practices were also promptly terminated at that time, and any employees who might have had knowledge of the situation were placed on leave, pending further investigation."  

A spokesperson for the school told CBS News Philadelphia, "With regard to Peak Performers, CCCS is still investigating what specific legal remedies are appropriate."