Sioux Trail Elementary students raised their milk cartons in the air and took one last swig of milk before recycling their cartons Wednesday. As part of a student-driven effort, the elementary students have reduced their milk waste by more than half at the school.

Student council members who go by the name of the “Moo Crew” are encouraging their peers to drink every last drop of milk before the end of their meals. The crew has gotten its message across by spending the year making posters and sharing facts about the health benefits of milk.

Before their campaign got rolling, Mark Glende, the school custodian, said the Burnsville school was on track to waste about 20 gallons of milk a week. The students brought that number down to less than 8 gallons a week, he said.

Glende would know. He weighs the waste bucket, a piquant combination of leftover milk, juice and water, six times a day after every breakfast and lunch.

In October, Glende began to notice that students were filling up the bucket at the end of lunch by pouring out their milk. He decided to approach the principal, Shannon McParland, and the two decided to take the issue up with the student council.

McParland grew up on a dairy farm near St. Cloud and was taken with Glende’s idea to stop students from tossing out their milk.

“We believe that if you empower students, you make a difference in the world, so we brought it to student council,” she said.

With Glende’s help, the students got to work. Fourth-grader Hannah Isenberger, 10, and her herd of friends designed posters and put them up around the school. Her poster featured the exhortation, “Don’t leave a drip, 1 more sip.”

“It is very important for kids our age to get milk in our bodies and grow,” she said in an interview.

The council then designated days like “Two Sip Tuesdays” and “Finish Your Milk Fridays” to motivate their peers to drink more milk. On those days, the Moo Crew stands in front of the cafeteria and reads off a skit with facts about milk.

“I immediately started seeing results,” Glende said.

The students even made a milk meter to reach their goal of eliminating milk waste. Glende and the students have set a goal on the meter of not wasting more than 25 milk cartons a day.

Students have the option each day to take either skim milk, 1 percent milk or chocolate skim milk.

With the program, Glende said students are drinking even more milk. About 272 students now drink their milk, up from 210 students at the beginning of the year. Some students now take two cartons of milk with their lunches.

“We want our students to drink milk for the health reasons but we are not telling them you have to drink your milk,” he said. Glende said he motivates the students to finish all of their lunch, not just their milk.

Fourth-grader Savannah Lee, 10, drinks about two cartons a day. She said milk helps make you smarter.

“We have a lot of stuff happening in the afternoon, it helps you focus,” she said.

On Wednesday, the third-grade students left barely any milk in their cartons for Glende to weigh. Some students had to squeeze their cartons to get any milk into the bucket.

With children around the world living in hunger, Denise Engberg, student council supervisor, said she wanted to stress the importance of the mission to her students.

“They can’t take it for granted,” she said.

The students’ efforts got everyone into the project, McParland said. The school transformed its “I Love to Read” themed hallway into a milk carton castle.

“I was surprised at how much it made a difference,” she said. “Because I don’t think any of us thought if you have each kid take another sip it would make that much of an impact, but yet it did.”