We have high hopes for Chancellor David Banks, which makes his decision to let down NYC kids by sticking with a cockamamie new high-school application system all the more disappointing.

The latest rules for entry into the city’s most academically competitive high schools are pure sabotage, cooked up in the final days of Mayor Bill de Blasio’s term. He never had the courage to do it during eight years in office, and instead did it on the way out the door.

They arbitrarily put all kids with grade averages of 85 and higher into a random “top tier” lottery, making suckers of those who strove for all A’s and perfect attendance. This injustice will prompt even more students to leave the system.

It’s a gesture to “equity” advocates who demand simplistic answers to the troubling fact that Asian students do much better than their black counterparts. But rather than improve elementary schools, the Department of Education would rather get rid of tests.

Banks had the chance to scotch the plan, even saying last week that he was considering 11th-hour tweaks after a wave of parent outrage. But this week he blinked, figuring the necessary delay would cause even more pain.

The chancellor pretends “the consensus is clear: We must reform our enrollment and admissions policies and expand access to quality schools.” He surely knows that the only fair way to “expand access” is simply to create more “quality schools,” not this mess.

Letting de Blasio’s ineptitude stand was an unforced error. Let’s hope it’s Banks’ last one.