Destroy the city school system in order to “diversify” it: That’s the bottom-line advice from Mayor Bill de Blasio’s School Diversity Advisory Group.

Ending all Gifted & Talented education is the most obviously rotten idea: It’s sure to prompt white (and Asian) flight from the public schools, and so guarantee decreased diversity. On top of that, it would reduce opportunity for the black and Hispanic kids who benefit from these programs now.

Does G&T need fixing? Absolutely. Karol Markowitz pointed out in these pages years ago that it’s just plain nuts to base admission to citywide G&T schools solely on a single hour-long test for 4-year-olds.

And we’ve long supported calls from the likes of Bronx Borough President Ruben Diaz Jr. and Brooklyn Beep Eric Adams to expand these programs, including by adding more borough-based G&T classes to ensure that lower-income kids aren’t shut out.

Indeed, Post reporting indicates that the decades-long decline in G&T opportunities for black and Hispanic children is one cause for the drop in black and Hispanic admissions to the top high schools.

Critics now flag the Bloomberg-era shuttering (for poor enrollment) of 60 G&T programs in the Bronx, Queens and Brooklyn, but the shift started long before that. And driving it was the same ideology that’s behind de Blasio’s panel: an “anti-tracking movement” that insists children of all abilities and races should learn together — at all costs.

Hence the new recommendations to not only kill G&T, but also end all screening for middle-school admissions, stop any expansion of selective high schools and so on. That is, to chase every possibility of excellence from the system in the name of helping the children the schools now fail to educate.

All this fits the approach pushed by Chancellor Richard Carranza: He has suggested the city labels too many kids as gifted, cheered the move to end middle school screening in Brooklyn’s District 15 and denounced the race-blind test for admission to the selective high schools.

Yet even Carranza didn’t dare rush to embrace the recommendations, merely issuing a statement vowing to “ensure all students have access to a rich and rigorous education” (which happens to be his job). The mayor was even more noncommittal.

And United Federation of Teachers chief Mike Mulgrew outright announced, “We do not support the elimination of the city’s Gifted & Talented programs. We believe the programs need to be revamped and access to them expanded,” though the union does oppose the test for 4-year-olds.

When the UFT and The Post agree that a move is bad for New York’s children, it should be case closed. De Blasio and Carranza need to dump this report in the trash and finally start focusing on opening more good schools, and adding more excellent programs, for all the city’s kids.