It was a month before Christmas, and all through the class, no first-grader saw this coming — not a lie this vast.

An essay had been written by a child with care, calling Santa real. Soon, he’d be there.

But their substitute teacher could not be aloof, so she chose to dish out some hard truths: Saint Nick isn’t real, she told them, nor is the Elf on the Shelf, nor leprechauns, the Tooth Fairy or the Easter Bunny, or ...

“She proceeded to debunk all of it,” Rene Rovtar, superintendent of schools in Montville, N.J., told about the incident that outraged parents last week and put her district in the national spotlight.

In a letter to parents, who flooded online forums to share their children’s duress, Cedar Hill School Principal Michael J. Raj wrote that he had spoken with the unidentified teacher “regarding her poor judgment in making this proclamation.”

“As a father of four myself, I am truly aware of the sensitive nature of this announcement,” Raj said in the letter, which was shared with The Washington Post. The principal had written to parents so they would be “aware of the situation” and able to “take appropriate steps to maintain the childhood innocence of the holiday season” at home.

In a statement, Rovtar added: “The childhood wonder associated with all holidays and traditions is something I personally hold near and dear in my own heart.”

Rovtar told The Post that after the “Santa Matter,” the substitute no longer works for the district. Citing it as a “personnel matter,” Rovtar declined to clarify whether the teacher resigned or was fired.

Move over, war on Christmas; it’s time to fight the war on Santa. This yuletide predicament is not isolated to New Jersey. During the Cape Coral Festival of Lights in Florida, a man with a large sign walked around shouting “There’s no Santa Claus!” Actors Dax Shepard and Kristen Bell told Us Weekly that they decided to inform their daughters, ages 3 and 5, that Santa is “pretend.” And on Fox News this week, Sean Hannity made the tension a topic of debate on two separate segments.

Across the country, in schools and at home, holiday spirit is approaching its annual surge. Depending on their age, children are penning letters to Santa about his list or conducting handwriting analyses of gift labels under the tree. Some are believers; others are skeptics. And with Christmas so near, the adults in their lives are faced with a legitimate conundrum: Whose job is it to break the news about the big guy with the beard? And how do you keep the magic alive for some children when the magic was never there for others?

“Indeed, just like the parents, the teacher’s credibility is on the line in these situations,” wrote David Kyle Johnson, an associate professor of psychology at King’s College, in Psychology Today. “If the teacher knowingly lies to one student about Santa, but another student knows that Santa is not real, the other student may (justifiably) worry that the teacher is an idiot, or is lying about other subjects."

Johnson, who is best known for his strong beliefs that adults should be truthful with children about the existence of Santa Claus, argued in his article and on Hannity’s second segment that he supports a parent’s right to choose how to raise their children. “A teacher intentionally co-opting such a decision, unprompted, doesn’t seem right,” he wrote.

But — and this is where his psychological angle comes in — he does not believe a teacher is obligated to promote falsehoods on behalf of a child’s parents. “Teachers have an obligation to give their students true and factual information,” Johnson wrote. “If a parent decides to lie to their children about something, it’s not a teacher’s fault when that child comes to them as their student and asks for the truth — even if it is about Santa.”

He continued:

“For example, my wife (a teacher) told me just yesterday about a student whose mother lied to her and told her that the local nuclear power plant, whose stacks spews large amounts of steam into the air, was just ‘a cloud maker.’ If even a first-grader wrote that in a paper, I would feel compelled to correct them. And if the child’s trust in their parent is broken as a result, that’s the parent’s fault for lying — not the teacher’s fault for telling the truth. And that fact doesn’t change just because Santa is a popular or common lie.”

But other experts have argued that children, like adults, are just as capable discerning fact from fiction as adults. It’s why adults must provide extensive evidence of the Santa farce to keep kids believing, wrote Jacqueline D. Woolley, professor and chair of the psychology department at the University of Texas at Austin.

“There is no evidence that belief, and eventual disbelief in Santa, affects parental trust in any significant way,” Woolley wrote in the Conversation in 2016. “Furthermore, not only do children have the tools to ferret out the truth; but engaging with the Santa story may give them a chance to exercise these abilities."

In New Jersey, the Santa Truthers haven’t deterred Rovtar, the schools superintendent.

Last Friday, she posted a photo to Twitter of herself with a large white-bearded Santa.

Beside it, she wrote: “I believe.”