With Earth Day this week, two Dallas-area school districts are observing the enviro-holiday in a unique way: by hosting "Lean & Green Day," with an all-vegetarian spread for their school lunches.

Both Highland Park and Dallas will offer a number of courses, including one starring Beyond Meat, the ultra-convincing meat substitute whose believers include Microsoft founder Bill Gates. Highland Park's ISD will serve its veggie meal on Earth Day, April 22; Dallas ISD is going veg on April 30.

Here's Dallas ISD's April 30 menu:

• Baked ziti with whole grain pasta and meat sauce with Beyond Meat beef-free crumbles
• Enchiladas with whole grain flour tortillas, black beans, rice, cheese and chili sauce
• Mediterranean salad made with falafel, feta cheese, Romaine lettuce, cherry tomato and cucumber, served with flatbread
• Chicken salad sandwich made with Beyond Meat chicken-free strips, apple, grapes and celery

Highland Park ISD's April 22 menu:

• Mucho beef and bean burrito, made with Beyond Meat beef-free crumbles
• Spinach and cheese lasagna
• Steamed rice
• Steamed edamame

Eddie Garza, food policy manager for the Humane Society of the United States, which is helping coordinate the event, previewed some of the menu items to staff, students and parents. "It's exciting to see Dallas and Highland Park ISDs' child nutrition departments providing healthy, delicious and sustainable school lunches in honor of Earth Day," he says.

At Highland Park, food services coordinator Karen Jacobsen is folding the Earth Day meal into part of a monthly program she created called "Wild Card Wednesday."

"Every third Wednesday of the month, we do something off the menu, which the students look forward to, since it's not same thing over and over," she says. "I happened to look at the calendar and noticed it said Earth Day [and thought] 'Perfect! We'll give this a try.'"

The beef and bean burrito is a vegan recipe, posted online "so parents can see," she says. "It has taco seasoning and is quite tasty. We're also doing a cheese and spinach lasagna; we always try to have two, and edamame."

She anticipates a warm reception. "We have a fair increase in the number of vegetarian students," she says. "And you'd be surprised at the number of elementary students who eat edamame."

In early April, the 2015 Dietary Guidelines Advisory Committee for the USDA — a panel that helps set federal dietary guidelines — recommended for the first time ever that Americans eat less meat not only because it's healthier, but also because it's better for the environment. It set off the beef, pork and poultry industries, but the committee ultimately concluded that a vegan diet had the most potential health benefits.

In Dallas schools, meals already include regular vegetarian options, says Margaret Lopez from the district's nutrition services department.

"In our district, we have at least 75 different home languages," Lopez says. "We have people from around the world who may choose not to eat animal foods. In some of our schools, that requirement is very prominent. So that's why we always have some alternative.

"Fortunately, it is possible to get some nice complementary protein from a combination of legumes and grains."

For many of those students, lunch is crucial, because such a large number of Dallas ISD students rely on school lunches: 85 percent of elementary students and 65 percent of high school students, Lopez says.

"We have to make sure the kids will eat what we offer," she says. "This day is important because it's introducing them to something different."