Michigan school-shooting suspect Ethan Crumbley appeared in court Friday and waived his right to a preliminary hearing, hours before a judge refused to reduce his parents’ bond.

Crumbley, 15, appeared by video from jail for the brief 9 a.m. probable-cause hearing in Oakland County District Court in connection to the Nov. 30 slaughter at Oxford High School that left four students dead and seven other people injured.

Prosecutors in Michigan typically present evidence to show probable cause to send suspects to trial on felony charges, but the high-school sophomore waived his right to that stage.

Crumbley is charged with four counts of murder and other crimes as an adult and remains held without bond. He faces up to life in prison if convicted. He pleaded not guilty last month.

Friday’s brief hearing, which lasted less than 10 minutes, came several hours before lawyers for his parents, Jennifer and James Crumbley, unsuccessfully argued to Judge Julie Nicholson that the couple bond’s should be reduced from $500,000 to $100,000.

Defense lawyer Mariell Lehman said the pair, who appeared by video, would agree to wear a GPS monitor if released on bail and claimed the gun that their son allegedly used in the school shooting was not “freely accessible” to the disturbed teen, as prosecutors insist.

“In Ethan’s journal, which was provided in discovery, he explicitly states that he has to find where his dad hid the firearm,” Lehman said.

“That statement, from Ethan Crumbley in his own words, is kind of contrary to the false and misleading assertions that have been made by the prosecution in this case — the assertions that the firearm was freely accessible,” Lehman told Nicholson.

Lehman said Ethan’s parents also had no knowledge of reports that he had tortured animals and claimed that he carried out the sinister acts without their knowledge.

But Oakland County Prosecutor Karen McDonald told Nicholson the Crumbleys constitute a “serious risk of flight,” as she urged the judge to deny their bond motion.

The Crumbleys, who have been in custody since Dec. 4, have since put their home up for sale and told relatives in Florida to sell horses they own in an attempt to stockpile assets, McDonald said.

They also have weak remaining ties to the community, the prosecutor said. James has “discretionary” employment as a DoorDash deliveryman, while Jennifer has been fired from her job since she was charged, McDonald said.

Nicholson ultimately cited the couple’s ties to Florida and their prior criminal conviction in the state as reasons for her denial. The judge also noted that they failed to surrender to authorities once they were charged and withdrew thousands of dollars beforehand. 

McDonald said the pair even took out $3,000 from Ethan’s account, leaving him with just 99 cents.

“The bond as set is reasonable,” said Nicholson, who scheduled another preliminary hearing for the couple Feb. 8.

The pair, who have been charged with four counts of involuntary manslaughter, are accused of allowing their son to get the 9mm handgun he allegedly used in the mass shooting and ignoring key warning signs ahead of the massacre. 

“The last thing they expected was that a school shooting would take place, or that their son would be responsible,” defense lawyers Shannon Smith and Mariell Lehman previously wrote in a court filing.

The couple, who have pleaded not guilty, face a potential of up to 60 years in prison if convicted on all counts. Prosecutors previously noted in court filings that the couple was missing for hours when charges were announced on Dec. 3 before police found them miles away in a Detroit art studio early the next morning.

Prosecutors have detailed how 45-year-old dad James bought the handgun his son allegedly used for the slaughter just four days beforehand — on Black Friday — as an early Christmas present for the teen.

The morning of the shooting, the teen’s parents were both then called in to meet with school officials who were alarmed at their son’s behavior, showing them distressing drawings of a shooting, with the words “help me” and “the thoughts won’t stop.”

But the parents insisted their son remain in classes — with the teen allegedly already hiding in his backpack the gun he used to kill Hana St. Juliana, 14, Madisyn Baldwin, 17, Tate Myre, 16, and Justin Shilling, 17.

Prosecutors have alleged that Crumbley’s parents ignored other disturbing behavior — including their son “torturing animals” and “even leaving a baby bird’s head in a jar on his bedroom floor, which he later took and placed in a school bathroom.”

All three Crumbleys are being held in Oakland County Jail, where they have been kept apart and are forbidden to discuss the case together.

Students at Oxford High School, about 30 miles north of Detroit, are expected to return to classes Monday for the first time since the shooting starting — but will do so at a different building. The school may reopen during the week of Jan. 24, but only after families have the chance to visit, the district’s superintendent has said.

With Post wires