Jenna Bush Hager's 5-year-old pranked his mom after his first day of Pre-K.Nathan Congleton / TODAY

Jenna Bush Hager's son, Hal, has gotten over his first-day-of-school jitters, pulling a classic prank on his mom.

"Our kids had their first day yesterday, which went overall pretty great," Jenna told her TODAY co-host Hoda Kotb on Sept. 5. about her children, Mila, 11, Poppy, 9, and Henry (Hal), 5.

"I picked Hal up and Mila was with me, and I said, 'Hal, how was school?' And he said, 'Pretty good, but I went to the principal's office,'" she said. "I was like, day one -- I mean, the school day was like, 12 minutes."

Jenna probed more. "I go, 'OK, so why did you go to the principal's office?'" and Hal's response was, 'I squirted apple sauce.'"

"It sounded like it was an accident ... and Mila looked at me like, 'He's lying,'" said Jenna. She told Hal that she would speak to his pre-K teacher about the incident during back-to-school night and Hal panicked.

"He knew he was busted," she said, adding that Hal confessed, "'JK (just kidding), I had the best day ever!'"

Hoda responded, "Your son is already messing with you."

Jenna referred to an on-screen photo of Hal holding his "first day of school" sign as a "mugshot," adding, "That little kid told me he went to the principal's office on day one, just as a joke."

Hoda shared a trick she uses on her daughters, Haley, 7, and Hope, 4, to encourage them to be truthful.

"I used to tell the kids that we had cameras in the house," said Hoda.

"Oh, we do that," said Jenna, adding that she tells Hal that the camera in his bedroom is actually a "smoke detector."

Hoda admitted that her daughters called her bluff by asking to see the camera.

"Are we the same people?" Jenna asked Hoda.

While Hoda said she confessed the truth to her daughters, Jenna said Hal is none the wiser. "Hal doesn't know, so let's not show him."

On Sept. 4, Jenna's children were nervous about their first day of school. Mila started 6th grade, Poppy 3rd grade and Hal pre-K.

"It's OK to be nervous," Jenna told her kids.

"Mila's like, 'How am I going to find 6th grade? I have to walk around, how am I going to find my class?'" said Jenna. "I was like, 'I'm telling you, I walked in, my knees were shaking.' And Hal was like, 'You were?' Because it's OK to be nervous!"