Second-graders at St. Catherine of Siena were practically bursting with information to complete their end-of-year tests, but it was teaching assistant Kylie Granger who had to answer the really big question.

Even taken by surprise, she didn’t have to think long.

With Ray Duplantier down on one knee and a diamond ring in his hand, and with family, friends, colleagues and 26 7-year-olds looking on, she said “yes.”

“It was her first year teaching there and she loves the kids, and so I wanted to include them,” Duplantier said recently of his May 20 proposal. “We’d already picked out the ring. I had to surprise her some way.”

Granger thought that students at the Metairie school might throw a celebration — her birthday was the next day. But she had no clue that Duplantier had phoned lead teacher Michele Williams with a request to make the party a ruse for him to pop the question.

As the school day moved toward its end, Williams asked Granger to go manage another class for an hour, because its teacher was out. Only 20 minutes had gone by, though, when someone came to relieve her, Granger said.

Suspicions aroused, she walked back to her own class. There, she peeked in the window and saw the kids lined up across the back of the room, each holding something.

As she entered, the excited students held up signs: The individual letters spelled out “Happy Birthday Kylie.”

Mystery solved, Granger thought.

But with a gesture from Williams, the youngsters flipped over their cards. The message now read, “Will you marry me?”

“He (Duplantier) had it set up so that when I walked in, he was behind me,” Granger said. “(Then) he was there with the ring.”

Her mother and sister were there, too.

“Everyone was screaming and cheering. In the doorway were 25 staff workers; everyone knew about it. The ladies in the office said they had the hardest time not telling me what was going on,” Granger said.

The kids, however, had learned about the proposal only after Granger left them to help out in the other classroom. Her absence gave them a little time to practice their all-important card-flipping skills.

“They got excited,” Duplantier said. “A couple of the girls were jumping up and down.”

Their reactions after Granger said “yes” were high energy as well.

“They were like, ‘Oh my God, she kissed him!’ ” Granger said, laughing.

“ ‘Can I get invited to the wedding?’

“ ‘Are you getting married in Vegas?’

“They were all telling their parents that I got married, but no, it was a proposal. The principal said it was the first proposal there ever, and it (the school) has been there since 1926,” she added.

A key player in the success of the surprise was room mother Christi Rice. Hearing of the plan from Williams, Rice promised Duplantier that she’d handle everything. She spent hours making the elaborate signs for the kids.

“She had my back covered. I’m not the craftiest person. She had glitter letters going. I’d have had a Sharpie,” Duplantier said.

The couple will marry in March at St. Catherine of Siena church.

“I originally signed up to work summer camp (at the school),” Granger said. “Then I thought, ‘What was I thinking? I don’t have time for this.’ ”