The peanut butter gives the student enough protein and milk provides the calcium, Reynolds said.
Many schools get money from the Washington County Board of Education to set up a fund to pay for lunches, but the money is expected to be returned, said Reynolds.
Local Parent Teacher Association officials agreed the fare is sufficient.
"There's a lot of people who live off peanut butter sandwiches," said Teri Williamson, president of the Washington County Council of PTAs.
"I personally like peanut butter sandwiches. It's not like they're doing it five days a week," said Boonsboro Mayor Charles F. "Skip" Kauffman Jr.
About seven students are served peanut butter sandwiches every week, said Reynolds.
Students used to be allowed charge their $1.30 lunch and then pay back the school later. But the school discontinued the program last year after it ended up "paying for a lot of lunches," said Reynolds.
The school has also set up an account system where parents can deposit money into a fund to pay for their children's meals when they forget lunch money, said Reynolds.
School officials were unaware of any other schools that have a plan like Boonsboro's.