Susan Cozza, Christine Skornia and Danette Eckelkamp, teachers at St. Gertrude School in Krakow, were expecting a day of emotional highs and lows when they took a group of seventh-graders last month on a field trip to the Holocaust Museum and Learning Center in St. Louis.

The students had just finished reading a book on the Holocaust, “The Boy Who Dared,” so visiting the museum, where they would also meet with and hear from an actual Holocaust survivor, was a chance to extend the lesson, give it a new dimension for them.

What the teachers didn’t expect, however, was an opportunity to take the lesson in an entirely new direction. That came up after they had left the museum, as the group of 30 students and 10 adult chaperones were eating lunch at El Agave, a Mexican restaurant in Pacific.

More than just a treat, the lunch was another learning opportunity, said Cozza, noting the students, who all take Spanish from Eckelkamp at St. Gertrude, were ordering their meals in Spanish.

After the meal, as Cozza was preparing to pay the $500-plus bill with money she had collected from all of the students and adults, is when it happened.

“I had a wad of money ready to pay when the waiter said, ‘It’s already been taken care of,’ ” Cozza recalled.

“He pointed to the parking lot and said, ‘That lady picked up your tab.’ ”

Cozza hurried out the door to catch the lady getting into her car. She wanted to say thank you and find out why the woman had been so generous.

“She was a retired teacher from St. Charles and said she was so impressed with our students — their behavior, such good manners — that she just wanted to do this,” Cozza recalled. “She wanted to pay it forward.”

The woman, who prefers to remain anonymous, even hoping she could get away from the restaurant before Cozza and her students learned of her gift to them, said she knows it takes a number of people — “good parents, good teachers and good principal” — to raise such well-behaved students that she wanted to do something to give back.

“She had been a teacher for over 25 years . . . and she said it was the least she could do,” Cozza commented.

Everyone in the group from St. Gertrude was stunned by the woman’s unexpected generosity.

“We were all so surprised,” said Skornia. “That’s a lot of money. It was good for the kids though, to experience someone paying it forward like that.”

In talking with the students about what had happened, Cozza learned that the woman had spoken with several of the students during the meal.

“She told us she had taught seventh grade and she was impressed by our behavior,” said Elizabeth Roellig.

“She told us how nice we were,” Mya Kemper added.

The students, who had been feeling a bit somber and reflective after their visit to the Holocaust Museum, were struck by the woman’s generosity even more.

“We had just learned about how cruel some people in this world can be and then we had an example of how nice someone else can be . . . ,” one student commented. “It made me want to be a good person.”

It had been hard to imagine the horrors of the Holocaust that they had read about in “The Boy Who Dared,” but hearing the survivor share his story made the decades-old atrocities feel all too present day.

Then just hours later to have someone extend such unwarranted kindness to them left an impression. It made the students want to do something kind for others.

“We came back to school and talked about it, and the kids wrote ideas of how we could pay this forward,” said Cozza. “They had a lot of good ideas, but most were geared toward doing volunteer work.”

The students settled on giving their time at three local free community meal events. They have volunteered at the monthly soup kitchen at Word of Life Church of the Nazarene in Union (held the first Monday each month, 5-7 p.m.); at The Welcome Table (on Tuesday evenings, 6-7 p.m.) free weekly meal offered at First Presbyterian Church in Union; and at The Harvest Table free weekly meal (on Saturday evenings, 5-6 p.m.) at St. Peter’s United Church of Christ in Washington.

In addition to volunteering their time at the meals, the students also made cash donations using the money they would have used to pay their bill at the restaurant.

Finally, the students have written thank-you notes to their benefactor and have invited her to attend an appreciation day for volunteers at their school.

“She really brightened our day,” said Claire Guehne. “We had been kind of depressed after being at the Holocaust Museum.”

Back at school, Eckelkamp asked the students to contrast the two experiences — their visit to the Holocaust Museum and the woman’s generosity in paying their $500-plus restaurant bill.

“Does it change the kind of person you want to be?” she asked them. “We all have choices we make every single day. What does her world look like?”

“Happy . . . sunny . . . friendly,” the class responded.

Now they hope they’ve paid that world view forward for others.