Minnetonka Public School officials say they've determined that a 17-year-old boy recently found working at a school construction site was the son of one the subcontractors and authorized to be there.

Furthermore, school officials say, Minnesota law permits a 17-year-old to work for a parent-owned business.

"In Minnetonka, we have many independent, family-owned businesses where teens gain valuable experience and work ethic during summer employment," school officials said in a statement. "This situation of the 17 year old son assisting his dad is no different. It is unfortunate that a union activist was harassing the teen on a job site."

Laborers International Union of North America 563 filed a complaint this week alleging child labor was being used at the Minnetonka construction site.

Two weeks ago, it filed a similar complaint involving a minor working at Cornelia Elementary in Edina. The school district investigated the incident have been assured by it contractor that minors won't work at the site.

Union officials say the two incidents are proof that there's a "disturbing trend" of contractors using child labor at school construction sites.

Several Minnesota school districts are adding classrooms or modifying space in schools this summer to accommodate for all-day kindergarten next year.