The head of an elite New Jersey prep school that has faced teacher backlash over its use of critical race theory has abruptly resigned, The Post has learned.

Rodney De Jarnett, who led Dwight-Englewood School in Bergen County, stepped down “effective immediately” amid an investigation into conduct inconsistent with the private prep school’s “values and standards of behavior,” administrators told parents in an email Monday.

“We want to assure our school community that the identified conduct did not involve our students,” the message continued. “The [Board of Trustees] cannot provide additional information because of the confidential nature of the independent investigation.”

De Jarnett had previously announced that he planned to retire in June 2023 after 16 years as head of Dwight-Engelwood.

A message seeking additional comment from a spokeswoman at the pre-K-12 school — where tuition can run as much $54,500 annually — was not immediately returned early Tuesday. Attempts to reach De Jarnett were unsuccessful.

The resignation comes less than a year after an English teacher at Dwight-Engelwood accused the school of using critical race theory to create a “hostile culture of conformity and fear,” leading white and male students to believe they’re “oppressors” while cutting off free speech.

“The school’s ideology requires students to see themselves not as individuals, but as representatives of a group, forcing them to adopt the status of privilege or victimhood,” the teacher, Dana Stangel-Plowe, wrote in a letter to school brass.

“As a result, students arrive in my classroom accepting this theory as fact: People born with less melanin in their skin are oppressors, and people born with more melanin in their skin are oppressed. Men are oppressors, women are oppressed, and so on,” the teacher’s charged letter continued.

Stangel-Plowe, who resigned over her CRT-related concerns, also claimed De Jarnett told the entire faculty on two occasions in 2017 and 2018 that he would “fire us all if he could so that he could replace us with people of color.”

The miffed educator also detailed a faculty meeting last year that was “segregated by skin color” and at which white teachers were told “to remember” and take responsibility for their power and privilege.

The mother of one student at the school told The Post some parents wondered why De Jarnett wasn’t ousted last year amid reports of critical race theory being taught in classrooms.

Counseling services will be offered to faculty, staff and students in the aftermath of De Jarnett’s early exit, according to board of trustees president Rob Miller’s message to parents Monday.

“Although this transition is occurring sooner than expected, we want to assure you the school is well positioned for the future,” Miller wrote, adding that a new head of school will be named within weeks. “We look forward to a bright future for Dwight-Engelwood.”