Mayor Bill de Blasio implied Sunday that he’s on a mission from God with his controversial plan to scrap the admission test for the city’s top high schools — and he just can’t fathom why everyone isn’t singing from the same hymnal.

The mayor repeatedly referenced the Bible in a visit to a predominantly black church in East Harlem, where he preached that his proposal would increase racial and ethnic diversity at the eight selective schools.

“Blessed are those who act justly,” de Blasio told worshippers at the Bethel Gospel Academy, referring to his plan.

In addition to quoting from Psalm 106:3, the mayor even likened his opponents to the apostle who questioned the resurrection of Jesus.

“I think scripture also tells us about the naysayers and the doubting Thomases,” said de Blasio, who’s described himself as “spiritual” while discussing his own beliefs.

The congregation drowned out the mayor with applause and a shaking tambourine when he said he would immediately boost the number of spots set aside for poor students who narrowly miss the test cutoff — even though 45 percent at the elite eight currently qualify for free lunches.

“Twenty percent of the seats will now be reserved for disadvantaged students to give them a chance to — ” de Blasio said before being muffled.

Currently, about 5 percent of students at the city’s eight specialized high schools get in through the “Discovery Program,” based on their test scores and family income, but de Blasio wants to boost that to 20 percent and add the requirement that they come from “high-poverty” middle schools.

The mayor continued his pious allusions during an afternoon news conference in Brooklyn, where he was joined by about 50 elected officials and community leaders.

De Blasio — who teased his plan in a Saturday op-ed for the Chalkbeat website — said not enough students were taking the Department of Education’s “Specialized High School Admission Test” because few parents knew about it.

“I have never accused the DOE of communicating well with parents. Can I get an amen?” de Blasio said, still feeling the spirit.

De Blasio — whose son, Dante, graduated from Brooklyn Tech, one of the top three specialized schools, and is now attending Yale University — also claimed he was pushing this plank in his progressive agenda because “the stars have now aligned” following his re-election last year.

“I’ve got a new mandate from the voters. I have a new chancellor who is focused on social justice,” he said, referring to recently installed schools Chancellor Richard Carranza.

Under the proposal, which would require approval of state lawmakers, the admission test would be phased out altogether over three years, with 90 to 95 percent of seats in the elite schools eventually reserved for the top 7 percent of seventh-graders from each middle school, based on a “composite score” of their grades and standardized test scores.

The remaining spots would go — via lottery — to students from religious and private schools, students who had just moved to the city and students “with a minimum grade point average who are not in the top 7 percent pool.”

Officials predicted it would raise the total proportion of black and Hispanic students from 9 to 45 percent, and female students from 44 to 62 percent.

But there are competing bills in Albany to either do away with the test or create a “pre-specialized high schools admissions test and preparation program” to get more students ready for and aware of the test.

Critics immediately attacked de Blasio’s plan for seeking to raise up disadvantaged students by lowering the bar instead of improving the educational opportunities in lower grades.

“The mayor is mistaken in his approach. Lowering the standards is not the way to go,” said state Sen. Diane Savino (D-SI, Brooklyn).

She noted that the state has given the city millions of dollars to offer free tutoring and test prep for the admissions exam, and accused de Blasio of failing to aggressively market the program.

State Sen. Toby Stavisky (D-Queens), a former Brooklyn Tech teacher, accused de Blasio of “assuming that young people who are black or Latino cannot pass the exam — and that is just not the case.”

“The answer is better training for kids. You have to do it at an earlier age. That will improve the end result,” said Stavisky, who’s sponsoring a bill for the pre-test prep program.

Eric Nadelstern, who served as deputy schools chancellor under predecessor Mayor Michael Bloomberg, predicted de Blasio’s proposal would prove too divisive to win approval.

“It isn’t a very clever idea. It sounds like a quota,” he said.

In a joint statement, the Stuyvesant and Brooklyn Tech alumni associations called de Blasio’s proposal “absolutely not the answer to this very complicated issue,” and said it would give “unprecedented, subjective control of admissions through the inclusion of new ‘multiple measures’ of achievement.”

Soo Kim, president of the Stuyvesant association, said de Blasio would unfairly disenfranchise many poor Asian kids, who account for a disproportionate number of the city’s top students.

“We are absolutely on the side of equity,” he said.

“But we don’t believe that the solution is taking from one needy community and giving to another needy community.“

Brooklyn Tech foundation president Larry Cary also said de Blasio’s plan would unfairly limit the number of students who gain admission from parochial and private schools.

“We have no place for anti-Catholic, anti-Jewish and anti-Muslim prejudice in our society or city and we should not want to discriminate against parents who chose a religious or private education for their children but wish to return to the public system,” he said.

The Albany legislation to do away with the test was introduced late Friday by Assemblyman Charles Barron (D-Brooklyn), who was among those at de Blasio’s news conference at JHS 292 Margaret S. Douglas in East New York.

“About the bill, you know, I know we talked about bootstraps and I understand that concept, but it’s about all of us rising — so when an individual makes it, you have not made it until all of us have made it,” Barron said at the de Blasio press conference.

Barron’s wife, City Councilwoman Inez Barron (D-Brooklyn), said: “What redlining was in housing, that’s what the single-measure test is in education, so we’ve got to eliminate it.”

Gov. Andrew Cuomo ducked the issue when questioned about it at the annual Celebrate Israel parade in Manhattan, quickly pivoting to the subject of education funding.

“I think the question on admissions and how schools are segregated, desegregated, is a very important issue. I also think funding equity is very important and how much we are funding each school,” he said.

Additional reporting by Carl Campanile