As the Jewish holidays enter the home stretch this week, another season of religious observance awaits many New York parents: Weekend after weekend of bar and bat mitzvah extravaganzas.

For those New Yorkers with children in sixth and eighth — but predominantly seventh — grades, a huge chunk of the upcoming weekends will be spent ferrying children to and from synagogue in the morning, and then to and from lavish parties that celebrate the time when young men and women become members of the Jewish community.

When parents complain to me about these black tie parties that feel more like weddings than bar mitzvahs — or ask me what I think about the messages they send to adolescents when parents spend six figures on excessive celebrations — I respond that there’s nothing new under the sun. I can remember attending lavish affairs at the Waldorf, the Pierre, and swanky clubs such as Regine’s, to celebrate my classmates’ rites of passage.

But recently, I heard a newsy tidbit about the bar and bat mitzvah circuit that made my jaw drop. It turns out that some 12- and 13-year-old children are inviting people they’ve never met to their bar and bat mitzvahs, either because they need to balance out the number of girls or boys in attendance, or because a specifically hot girl or guy will add a certain je ne sais quoi to the party.

“A lot of the girls and boys at the single-sex schools don’t know many kids of the opposite sex,” a mother of two girls who attend a single-sex school on the Upper East Side told me. “So, a friend planning her son’s bar mitzvah, for example, will call you and ask if she can Xerox your class list. She’ll then let her kid go through the list, and decide who to invite. The kids recognize each other’s names and have met each other at dances in sixth grade or other bar mitzvahs.”

Do parents allow their children to attend parties given by families they don’t know — and to celebrate children they’ve never met before?

“Most parents let their kids go,” the mother told me. “The kids are so worried about having their bar mitzvah parties be fun. And a party with 30 boys and five girls, or vice versa, isn’t going to be great, so the parents are sympathetic to the kids’ anxieties.” She also added that children can figure out who unknown students are, and what their families are like, through degrees of separation.

Another mother of two boys at a single-sex school said that she is disturbed by this phenomenon. “I think it’s terrible that the parents allow their children to invite people they’ve never met to the parties, and terrible that other parents allow their children to go to parties where they don’t know the parents or children,” she said. “This is, after all, a religious function.”

Another mother said that it’s one thing to spend her weekend taking her son to and from parties of children he’s in school with. “It’s another thing, though, to ruin my weekend taking him to and from a kid’s party that he’s never met,” she said.

I spoke to a few of my friends who went to single-sex schools back when I was busy gussying myself up for galas at Regine’s. They were just as shocked.

“My parents never would have let me invite boys I didn’t know to my bat mitzvah,” a Spence alumna told me. “Of course there were more girls at my bat mitzvah than boys. That’s just the way it was.”

“We definitely knew all the kids at each other’s parties,” a Chapin graduate said. “There weren’t that many Jewish kids in our classes, though, maybe 5 out of 32, or so. Today, I hear there are more.”

A headmaster at one of the private all-boys schools said that the class lists are meant to be only for school parents. “There’s not much we can do to enforce this,” he said. “Of course we would hope that parents have enough common sense to keep this kind of private information to themselves.”

One 13-year-old girl I spoke to said that the girls are more concerned with having enough guys than vice versa. “The girls are definitely impressed if you have lots of boys at your parties,” she said. “There are, like, one or two girls who get invited to every party, because the boys are in love with them. But most boys are less worried about their parties than the girls.”