Every San Francisco kid will get a free field trip to the California Academy of Sciences every year of elementary school in perpetuity — transportation, tickets and time to study penguins, pipefish and leafy seadragons included — thanks to a unique $20 million gift to be announced Monday.

Academy officials say the funding provided by philanthropists Arthur and Toni Rembe Rock will ultimately serve about 28,000 public and private school kids annually.

An existing endowment of $11 million has offered the free trips to fourth- and fifth-graders, but Monday’s announcement includes a $9 million increase to expand the program to all students from kindergarten through fifth grade.

The funding means city elementary schools will never have to scramble to raise funds to take a field trip to learn about rain forests, rocks and minerals, coral reefs or Claude the albino alligator, said Elizabeth Babcock, the academy’s chief public engagement officer.

“We are so thrilled this opportunity will exist for every single kindergarten through fifth-grader, and their teachers and their parents,” Babcock said. “This is saying science and environmental learning is for every single kid — no matter what neighborhood, what background, what school they go to.”

Teacher Elvira Walden has been taking her fourth-grade students at Ulloa Elementary to the academy for years, knowing the trip was free and the students would discover something new and exciting. This year’s class went in December.

“Even if you’ve been there 10 times, you still get a different experience every time you go,” she said. “They really do see it through fresh eyes every time.”

Walden said she loves seeing what excites children — which is sometimes the unexpected, like a geology exhibit with a bunch of rocks.

“If we just let them explore and watch and inquire, that is really what that place is,” she said. “It is just magic.”

The endowment will provide on-site science lessons led by academy educators, educational take-home materials in multiple languages, and free teacher workshops. In addition, it will cover a free family night, allowing students to bring their parents and siblings back for a visit. Elementary school students will also gain unlimited free admission during the school year.

“By supporting early science education and leveling the playing field for every student in San Francisco, we’re ensuring that all students can benefit from the transformative experience of an academy field trip,” Arthur Rock said. “We’re also creating a model partnership between a cultural organization and local schools that we hope will inspire similar collaborations in cities across the country.”

The academy will phase in the expansion of the Rock Program through 2022. Currently, about 95 percent of San Francisco public school fourth- and fifth-graders participate in the annual free field trips.

“The California Academy of Sciences is primary among the organizations that take students outside their conventional classroom settings to make science come alive,” said Jim Ryan, executive director of science and math education at San Francisco Unified School District. “Through these types of partnerships and generosity we will raise a generation of science-literate and civically engaged San Franciscans.”

Babcock said she wants the children of San Francisco to feel as though they belong at the academy.

“Year after year, there’s no higher reward as an educator than to watch young minds blossom during a field trip to the academy,” she said. “Children are natural scientists — asking questions, exploring their surroundings and letting their curiosity lead.”