Ruben Mendoza opens the heavy door for two small students who have arrived early for school. “Welcome,” he says quietly, inclining a bit to envelop them in the warmth of his smile.

A welcoming spirit is just one of the gifts Mr. Mendoza, Head Custodian of Washington School, has bestowed on the school in his more than 25 years there. Having immigrated to Evanston in 1977 from Huatzindeo, a small village in Guanajuato, Mexico, he understands the challenges of acquiring a new language and customs – and the value of a friendly greeting.

Long before School District 65 introduced bilingual classes and social workers or adopted the Two Way Immersion program known as TWI, Mr. Mendoza addressed the communication gap between English-speaking teachers and Hispanic parents by offering to translate – on his own time – at parent-teacher conferences. “There were not a lot of Spanish-speakers at Washington in those days,” he says. “I used to help the teachers a lot.” He gave willingly but admits “it was sometimes a struggle to do my job and translate.”

His help did not go unnoticed. A woman who attended Washington a quarter century ago recently reencountered Mr. Mendoza and recalled his generous contribution in a Facebook entry: “I got choked up, talking to him, as I remembered this tender service of his, so long ago.”

Though nowadays the school has in place various supports for Spanish-speaking immigrants, Mr. Mendoza is still a friend who can help bridge the gap between their old and new homes. “Every Hispanic kid [at Washington], I know them,” he says. “Almost on every corner they know me.”

He marvels that nowadays “they speak English in my [Mexican] village,” where fourth grade was the last schooling for most children of his generation. It was once his dream, he says, “to come to the U.S. and go back [to Mexico] and work in San Miguel de Allende.”

But in 1979, the year after he arrived, Mr. Mendoza met his wife on an Evanston playground and changed his dream. He did not return to Huatzindeo until 1990; he and his wife had four daughters, and, he says, “My life was here.” It was easier to pay for his parents to come to Evanston than to go to them, he says.

He still seems amazed that he, who “did not even go to high school,” landed “this job” he obviously loves. He talks about “seeing the kids” – 500 a year – and alludes to the vacuums and up-to-date tools of his trade as though they were toys. “With me, it’s a game,” he says. “It’s fun.”

It is no secret that, despite his easy-going ways, Mr. Mendoza “is a hard worker,” says Sandra Jimenez, Washington School secretary. In addition, she says, “Ruben was like a father” to her daughter, who worked in the school office with her for 10 years.

Mr. Mendoza “is one of the most dedicated of the District 65 custodial staff,” says veteran third-grade teacher Rosa McAndrew, who lights up when asked to talk about him. “He takes great pride in the school,” she continues – a pride that only swelled when his daughters attended Washington.

He is quick to ask visitors, “Have you seen the building?” and to describe the stained glass windows and other wonders of the school. Built in 1898, Washington graduated its first class in 1901. An addition was completed in 1953, Mr. Mendoza says, and the former Park School was joined to the two older sections in 1985.

A custodian of the past as well as the present, Mr. Mendoza says he is saving some old books he rescued when Washington celebrated its centennial in 2001. Among them, he says, is “the original petition for the school,” dated 1898.

On a day in early September, this old building sparkles like new for the children starting another school year. They should know that Mr. Mendoza has put a polish on the outside of the building as well as the inside.

On the school grounds, where he says “there wasn’t even grass at all,” he started a garden. He began by planting throwaways from the former Frank’s Nursery at Dempster and Dodge. The plants proliferated and became many gardens – shade and sensory and pizza and herb gardens, among others. Children helped him plant bulbs. Eventually the PTA assumed responsibility for maintenance of the gardens, though Mr. Mendoza jokes that he “still works there instead of sleeping in my office” and admits he “comes over sometimes on Saturdays.”

A brick in the school sidewalk commemorates Mr. Mendoza’s role in the greening of Washington. And the most verdant garden of all – the tangle of tall milkweed and other native plants on the north side of the school – bears the name “Mendoza Prairie.”

Inspired by the butterfly garden Mr. Mendoza’s wife planted in their yard, the prairie offers Monarch butterflies the nutrition they need to fuel their incredible migration to Mexico and to make possible the return of the orange-and-black-winged Mexican immigrants Mr. Mendoza hopes to welcome next year.

He who watches over butterflies will not let a child go hungry. “If someone has no lunch, he finds one,” Ms. McAndrew says. “Mr. Mendoza is one of those extraordinary people – just a jewel.”