EASTPOINTE, Mich. -

Investigators say Jonathon Sails, the substitute teacher charged with involuntary manslaughter in connection to the drowning of 14-year-old KeAir Swift during a swim class at East Detroit High School last November, did not have the proper certification to be a swim instructor.

He had been put in charge of the class after the previous instructor's certification expired.

Sails was hired by Professional Educational Services Group, one of the largest staffing companies of its kind in the country. They have relationships with a long list of districts in Metro Detroit, according to their website.

Some parents are concerned about who may be subbing in their child's classroom in light of the circumstances surrounding KeAir's death.

"That's where they go to school. The time when they are not with their mother and father and they're supposed to be safe there," said parent Nichole Loper.

PESG says prospective substitute teachers must pass a "criminal history background check that excludes individuals with felonies and certain misdemeanors as outlined in the Michigan Revised School Code."

The company also conducts a "work history review." We're also told "certificates (teacher and administrator certificates), permits, and licenses are verified where appropriate."

No matter the checks, this parent knows it's no guarantee.

"People follow that career because they want to help children, they're not there to hurt anybody. Negligence can happen with anybody," said Robert Jessmon.