DETROIT — A 74-year-old businessman who sold supplies to the Detroit school district was sentenced to five years in prison Tuesday in a bribery and kickback scheme involving a dozen principals and one administrator.

Norman Shy told U.S. District Judge Victoria Roberts that he “made a horrible mistake” and accepts “full responsibility” in a scheme that defrauded the financially struggling district and its students out of $2.7 million. The government says Shy paid out about $900,000 in kickbacks.

“There are no words to express how horrible I feel and how embarrassed and ashamed I am,” Shy said in court.

Roberts said she wanted to send a message with Shy’s sentencing, despite his age.

“Any number of vendors now stand in the shoes of Mr. Shy,” she said. “They, too, may be tempted to enrich themselves. Deterrence of others is a laudable goal.”

She added: “Our children are priceless. They are entitled to every dime and every book sent their way. There simply is not an ethical credit for you to dodge a lengthy sentence.”

Shy also has to pay $2.7 million in restitution to the school district and more than $51,000 in back federal taxes.

The scheme spanned a number of years and involved bogus invoices that were submitted for chairs, paper and other supplies, some of which were never delivered. In return, gift cards, cash and checks were given to school employees. All but one of the principals has pleaded guilty.

“Former administrator Clara Flowers was sentenced Tuesday to three years in prison. She had pleaded guilty to accepting $325,000 in cash, gift cards and other favors.