Biology teacher India Aranha, of Gwynn Park High School in Prince George’s County, shows other teachers around her campus as they consider projects to foster environmental literacy. (Donna St. George/The Washington Post)

They tested the water quality in Baltimore’s harbor and again in the middle of the Chesapeake Bay. Near Smith Island, they dropped a scraping net, marveling over the biodiversity of what they pulled in: sea horses, puffer fish and sand shrimp.

For 18 Maryland teachers — and more than 225 others before them — the week of environmental immersion along the Maryland shore in August was geared toward a lofty-sounding goal: that Maryland students graduate with environmental literacy.

Maryland, which in 2011 became the first state in the nation to create such a requirement, has been expanding on the idea ever since. Environmental learning is integrated in the curriculum of its 24 school systems, and teacher training continues to be a focal point.

The Chesapeake Bay experience left many educators with a deeper understanding, they said. They conducted field tests aboard a work boat in the bay. They interviewed watermen and sampled the crab population. At the end, they worked on writing curriculum modules, an effort that will continue in the months ahead.

“I’m a lot more enthusiastic and much more inclined to give my students that same kind of hands-on experience,” said Rosetta Jordan, a biology teacher at Magruder High School in Montgomery County. “It’s different when you see it for yourself. . . . I felt like a little kid when we pulled up a puffer fish and sea horses. I had never held a sea horse in my hand.”

The teacher training helps to address one of the state’s key standards for environmental literacy — that students conduct an environmental-issues investigation and develop a local action project.

“We’re asking for a huge pedagogical shift, so it’s not a teacher-centered classroom but a ­student-centered classroom,” said Gary Hedges, the environmental education specialist for the Maryland State Department of Education.

Each school system takes its own approach to implementing the state standards but must certify how it has done so. Maryland officials say the Class of 2015 was the first to graduate having met its requirement. There is no new state testing linked to the literacy standards.

“The intent was that it would be this really robust, rich approach to environmental literacy that would include both content and instruction as well as meaningful experiences for the students,” said Sarah Bodor, who was deeply involved in the Maryland effort and is now policy director for the North American Association for Environmental Education.

The training for both science and social studies teachers comes as one of a number of efforts to help school systems meet the goal. It was provided by the Chesapeake Bay Foundation and the University of Maryland Center for Environmental Science as part of their work with the Maryland Environmental Literacy Partnership, which includes key state, federal, university and local partners.

“We want to make sure we are meeting not just the letter of the law but the spirit of the law,” said Tom Ackerman, vice president of education for the Chesapeake Bay Foundation. The August training, like other summer sessions over the past three years, brought teachers together from around the state.

“For me, it was an eye-opener,” said Olukayode Banmeke, a science teacher at DuVal High School in Prince George’s County who has made plans for more hands-on experiences for students in the coming school year.

Andrea Katkow, a Howard County science teacher, said she left the training with a strong sense of how much watermen and Smith Island residents depend on the health of the bay’s ecosystem for their way of life. She made video clips of question-and-answer sessions to show her students.

“Personal stories are something that students and kids relate to,” she said. “They are themselves social beings.”

Katkow said inquiry-based learning is not new, but the week of training provided a better idea of how it can be done. “It’s a different way of thinking,” she said. “It’s a different framework.”

As she and other teachers finished their week, they gathered in Prince George’s at Gwynn Park High School in Brandywine.

There, biology teacher India Aranha led teachers on a tour of her school’s grounds and talked about how to translate the experience to their own schools.

She and others said that every school’s site is ripe for environmental exploration and action — a place where trees can be planted, drainage problems resolved, gardens created. Gwynn Park has its own greenhouse, dating to a horticulture program that no longer exists. The hope is to expand it into a year-round operation.

“You can see the potential in it,” Aranha told the teachers as she urged them to think about what is possible at their own schools.

In Montgomery, most of the high school literacy standards are embedded in biology classes, said Laurie Jenkins, supervisor of K-12 environmental education. Some are also infused in government classes, where students choose an environmental issue, do research and ultimately write an advocacy letter, she said.

“We want them to become citizens who can make good environmental decisions,” she said.

In Prince George’s, Sylvester Conyers, supervisor of environmental education, said more than 80 percent of high schools have sent at least one teacher to summer training. Educators who have come back continue to work together and will ultimately refine their lessons, sharing them with other teachers so they all become proficient in providing students with an effective environmental education.

“It’s a way to engage students in not only learning about the environment but learning about the issues that affect the environment so that they can come up with possible solutions,” he said.