After the teenager spent time on the road with his mom, traveling for her recent Rebel Heart tour, he went to the U.K. to spend time with his father and reportedly refused to return to the U.S.
On Dec. 23, the "Living For Love" singer appeared in a New York City courtroom, where a judge ordered that Rocco return to the U.S. to sort out his living situation, the New York Daily News reported at the time.
But according to a source close to the singer, Rocco has yet to return home. Indeed, he spent Christmas and rang in the new year with Ritchie, 47, in England. Meanwhile in N.Y.C., Madonna, 57, spent Dec. 25 sharing festive photos of her other three kids – Lourdes, 19, David, 10, and Mercy, 9 – on Instagram. (She shared a throwback shot of Rocco as well, captioning it: "Merry X-mas to the Sun-shine of my Life.")
"He should have been home already," says the source, who alleges that Rocco has missed some school. "Madonna is a devoted mother, and a big priority is her children's education."
As for why the teen left his mom's tour, an industry insider says he "got tired of it and wanted to be home with his dad."
For more on Madonna and Guy Ritchie's ongoing custody battle, pick up the latest issue of PEOPLE, on newsstands Friday.
Up next, Madonna and Ritchie – who finalized their contentious divorce in 2008 – are due in court Feb. 3 for a second hearing in New York.
Lawyers for Madonna and Ritchie declined to comment.
With additional reporting by LIZ McNEIL and SARA NATHAN