Fourth-grader Kevin Johnson III bounced up and down with excitement as he belted out the words to “All I Want for Christmas is You” at his Baltimore elementary school’s winter concert.

“What more can I do,” the Bedford Elementary student, known as Knox, sang joyfully, “Baby all I want for Christmas is you.”

Knox smiled as he was handed a microphone for his solo. He hit the high notes. He danced around in a circle. He finished to cheers from the audience, and then ran towards his mom in tears of joy, The Washington Post reported.

“Just think of something happy and put that into your performance,” White-Johnson, in an interview with The Baltimore Banner, said she told Knox before the concert. “And I know that’s what he did.”

Proud of her son, White-Johnson took to social media last week to share a video of Knox’s performance. It quickly went viral.

“Timeline cleanse if you need one! Knox tonight at his 4th grade school winter concert singing @MariahCarey ‘All I Want For Christmas Is You’ #AutisticJoy on full display! My kid is everything! I hope Mariah sees this!!” White-Johnson tweeted.

More than 500 people shared White-Johnson’s tweet with their own followers, spreading Knox’s infectious joy across social media.

“Here’s some joy in your feed. Well done Knox! You are awesome,” one person tweeted.

“Inclusion is joyful,” another said. “All we want for Christmas is more of this — thank you Knox!”

Even Mariah Carey herself loved Knox’s performance, and re-tweeted the video on Wednesday.

“Your kid IS everything!!!!!! Knox, you made my day. Your JOY gives me and everyone watching JOY. THANK YOU for reminding me why I wake up in the morning and do what I do. I love you,” Carey tweeted.

The family had the tweet framed, White-Johnson shared in an Instagram post.

White-Johnson said she loves that more people are getting to see Knox’s joy, “because it’s something we see everyday,” she said. “In our eyes, he’s always been our famous Knox, and his ultimate goal in life is to make others happy, to spread that love... and we’re just excited that the world is getting to see that.”

The response, she said, is helping affirm to Knox that he doesn’t need to hold anything back. He can be joyful and happy and excited about who he is, and not be ashamed to celebrate it, White-Johnson said.

As he’s seen the articles and social media responses pile up, she said, he’s begun to realize: “I’m really famous! I’m famous!”

“This is glorious,” he told White-Johnson.

The video, White-Johnson said, has also been an opportunity “for different disabled and autistic voices to feel like they are being seen,” she said.

One parent, she said, shared in a comment that her daughter had a Christmas concert, and the director told her she wouldn’t be allowed to perform if she didn’t “stay really still and really calm.”

Knox started singing around age 3, White-Johnson said.

“Before he was even forming conversations where he could express his desires and his wants and needs, he was singing and expressing his joy through that,” she said.

Now, he sings everywhere he goes — in museums, at the park, in the bathroom, in the train station, at the grocery store, she said.

When Knox was around six, he had to be sedated to have dental work done — but that didn’t stop him from singing.

“We have a video of him literally in scrubs, in a hospital bed, singing ‘Rudolf the Red Nose Reindeer,’ ” White-Johnson said.

Some of his favorite tunes are from classic musicals such as “Hello, Dolly!” and Disney movies like “Lady and the Tramp,” she said, as well as Christmas carols.

And he loves to perform, White-Johnson said. As a toddler, Knox performed in holiday concerts at The Shafer Center, a school for children with autism in Owings Mills. At six, he belted out “Hark! The Herald Angels Sing” on stage at his church. At eight, he took piano lessons and performed his first recital, White-Johnson said. And at home, he loves to record sounds on GarageBand — and speed them up or slow it down, or add other sounds on top.

“He’ll make fun little loops or beats,” White-Johnson said. “He has such a beautiful musical ear.”

After his performance went viral, Knox has been featured on the Today Show and in Billboard Magazine, according to White-Johnson’s Instagram page.

Carey even invited Knox and White-Johnson to her holiday show at Madison Square Garden. The two watched it on TV, instead, White-Johnson said.

“I saw her in concert on the channel!” Knox said excitedly during a phone interview on Wednesday.

And how did he feel when he saw Carey loved his performance?

“I felt awesome. I felt so excited about that,” Knox said proudly.

cadence.quaranta@thebaltimorebanner.com