Just months before breaking ground for the expansion of the St. Stephen Lutheran Academy in Zelienople, Glade Run Lutheran Services of Zelienople, which owns the school, received word of its largest single donation ever.

The Richard King Mellon Foundation gave the project a $500,000 grant that will be used toward the $3.8 million project.

"We're just thrilled ... we are grateful,'' said Cindy Shafer, director of resource development at Glade Run, which has been working with the foundation the past year.

Butler County commissioners in December approved a $3.8 million bond for the Butler County Industrial Development Authority on behalf of Glade Run, which will be responsible for paying it back.

Ms. Shafer said Glade Run is trying to raise money as a way of covering the debt service on the project. A grant of $150,000 from the state Department of Health was awarded in April.

The project involves construction of a 20-classroom addition to the school. Two of the classrooms will be geared toward teaching children with autism. Ms. Shafer said a "sensory room" will allow students to "learn through experience." There also will be an apartment constructed as part of the project to teach independent living skills.

She said the expansion was prompted by an increased demand within the community for services that benefit children who are at risk.

"We have outgrown our current school space. The new classrooms will allow us to better serve current students and also those children on our waiting list in one centralized, educationally sound school facility," she said.

The school annually serves 430 students who have mental health and behavioral issues that preclude them from learning in a traditional classroom environment.

"We have the opportunity to provide a therapeutic setting in our classrooms that help these children learn and thrive in ways that work for them," Ms. Shafer said.

Of the new classrooms, 10 will be for new students while the other 10 will centralize classrooms that are currently scattered throughout the campus. A maximum of 12 students will be in each classroom.

Groundbreaking is expected within the next few months, Ms. Shafer said, and the school is to be open for the 2009-10 school year.

The school opened in 1993 on the 325-acre campus, which has 22 buildings associated with the school and Glade Run Lutheran Services.