It’s the Big Apple Grand Prix in city school zones now that the speed cameras have gone dark.

The Post counted dozens of lead-footed drivers zooming past Park Slope’s PS 124 on Thursday — all of whom would have gotten automatic $50 tickets had state legislators reupped the city’s speed cam law.

The city rolled out 140 of the cameras near schools in 2014 after receiving Albany lawmakers’ blessing.

But state Senate Republicans refused to take up a bill to renew and expand the program — which city officials say slows speeders by 63 percent — before the legislative session ended last month.

Without authorization, city officials switched off all but 20 of the cameras. The remainder are set to go dark at the end of August — days before the new school year.

“School is starting, and we need these cameras. Sometimes the crossing guards just aren’t enough,” said Naomi Quinones, 29, whose 9-year-old daughter attends PS 124 and whose 4-year-old son, Vincent, starts there in the fall.

“Just now at the corner of Fourth and 15th, I was walking with my son, and this guy ran a red light. I screamed ‘Vincent’ and stopped him. Thank God nothing happened, because I know my son likes to run away sometimes.”

In just 20 minutes at the corner of Fourth Avenue and 19th Street, The Post counted 51 out of 100 passing cars defying the law.

Three were moving at more than 36 mph — the minimum for the speed cams to issue a ticket.

But over the course of several hours, The Post tallied more than two dozen speed demons who should have earned citations.

The difference of a few miles per hour can mean the difference between life and death, according to figures from the city’s Department of Transportation.

A driver traveling at 40 mph needs 300 feet to perceive a hazard, react and brake in time — that’s twice the distance someone going 25 mph needs.

The Post counted two 40 mph- plus drivers — a BMW with the vanity license plate “GRIND” clocked at 41 mph and an FDNY pickup with no lights or sirens doing 45.

Pedestrians slammed by 30 mph vehicles are twice as likely to be killed as those hit by vehicles going the city’s 25-mph speed limit, officials said.

That statistic depends on the size of the vehicle, because larger vehicles — such as the Mack garbage truck The Post clocked at 31 mph Thursday — move with greater momentum.

“I realized how bad the problem was when I saw a young kid on a bike get hit by a car turning right onto the corner of Fourth and 16th street,” South Slope resident Tim Gramling, 36, said moments after stopping his 2-year-old daughter from careening into the intersection of Fourth and 19th on her scooter.

“Especially now that my daughter has started riding a scooter, it really makes me nervous to see all the speeding drivers in the neighborhood.”

Additional reporting by Tamar Lapin