There are legions of Jewish adults who look back on their youth, vastly inflate their athletic prowess and thrust an accusatory finger at an establishment that robbed them of a glorious sports career:

Hebrew School.

Two afternoons during the week, once more on Sunday morning, a time for Moses, making Seder plates and eating hamentashen. Time well spent, but time not spent refining foul shooting, hitting a baseball or, heaven forbid, anything having to do with shoulder pads and helmets.

Geoff Schwartz might have followed in the same footsteps of all the kids in those Alef and Bet classes, except his footsteps grew so big, as did the rest of his body, that at the age of 15 he finally was given the blessing to start seriously playing football. He’s doing it now for the Giants as their massive starting left guard, a key addition in the rebuilding of their offensive line, an NFL player who reached the heights after surviving a particularly daunting challenge.

“The so-called ‘Jewish mother’ thing,’’ Schwartz told The Post on Thursday while seated on and engulfing the better part of a sofa. “My dad never played football because he wasn’t allowed to. My grandmother was like, ‘You’re not playing football.’ It is just the way it is.’’

Bar Mitzvah lessons took precedence over studying the playbook for Schwartz while growing up in the Los Angeles area. He and his younger brother, Mitchell — a guard for the Browns — are the first Jewish brothers to play in the NFL since Ralph and Arnold Horween (also known as Horwitz) in 1923. There are only nine NFL players who identify themselves as Jewish, and the Schwartz boys are two of them.

“Every time there’s something in the Jewish Journal or when we see their parents it’s a topic of pride and conversation when we hear about our two NFL Jewish players,’’ said Rabbi Arye Berk of Adat Shalom in West Los Angeles, the synagogue where both Schwartz boys had their Bar Mitzvahs.

Growing up, Geoff, 28, and Mitchell, 25, did not go to school on the High Holidays, but incorporating observance and the religion of NFL football is more challenging. This season, the Giants face the Redskins in Washington on Sept. 25 — the first day of Rosh Hashanah, the Jewish New Year. Schwartz will make the trip and play in the game. The next week, he says, he will attend Kol Nidre services on Friday night but will not fast that night or throughout the day on Saturday for Yom Kippur.

“In the past, the year I was on [injured reserve] I fasted, I wasn’t playing,’’ Schwartz said. “I’ll go to services, but the fasting during the season, it’s got to be on Tuesday [the players’ day off]. The way I look at it is, I’m only playing football for a certain number of years and I kind of owe it to myself to kind of take advantage of it.’’

Parents Lee (a management consultant) and Olivia (an attorney) will fly in from LA to spend Yom Kippur with Geoff and his family, and then go to the game against the Falcons the next day at MetLife Stadium. That’s nothing new. Lee Schwartz said he and his wife have been to High Holiday services in Minnesota, Dallas, Reno, Nev., and Kansas City, wherever football has taken them.

“It makes us really happy and proud,’’ Lee Schwartz said. “We had a Jewish household and they went to religious school and we were part of a synagogue. We tried to bring the traditions home and raise them with a real Jewish identity.’’

On Dec. 21, the Giants will be in St. Louis to face the Rams, and Schwartz will bring his menorah with him and light the Hanukkah candles in his hotel room, a tradition he follows every year. When he played for the Vikings, he was joined on the road by a Jewish assistant coach, who said the prayers with him.

Last year, as a member of the Chiefs, he lit the Hanukkah candles and recited the blessings at the Chabad House in Kansas City and spoke at the Hyman Brand Hebrew Academy, the only Jewish day school in Kansas City, where he was presented with a personalized yarmulke emblazoned with his jersey number and Hebrew name, Gedalia, meaning “God is great.’’

“I definitely think you look at the past of Jews in sports, there aren’t many and we’re typically not of my size, particularly not the best athletes, it’s just kind of the way it’s been,’’ Schwartz said. “Seeing me and my brother and some other guys that are Jewish in baseball, we have some players who have really excelled, it does give people hope. I got lucky because of my genes.’’

His genes caused the need for bigger jeans. Lee is 6-foot-1, Olivia is 5-10 and Geoff’s paternal grandfather was 6 feet. Mitchell is 6-5 and 320, big but not as huge as Geoff, who is 6-6 and a beefy 340 pounds, with huge paws for hands and size 18 shoes. Schwartz played in college at Oregon, was a 2008 seventh-round draft pick of the Panthers and has bounced from Carolina to Minnesota to Kansas City, not yet finding a football home. He hopes he’s got one now after signing a four-year, $16.8 million contract with the Giants.

An aspiring chef, Schwartz loves to cook and eat Jewish delicacies, and although he doesn’t keep kosher, he is excited about living in an area where he can get genuine matzo ball soup.

Since he has been in the New York/New Jersey area, he already has felt the strong Jewish vibe. He has been asked to speak at synagogues, “lots of invites to Shabbos dinner’’ and, recently, filled a fairly unusual request. He made a video chanting the HaMotzi — the blessing over bread — and on May 3 it was played at the Bat Mitzvah of Emily Hanlon, the daughter of Pat Hanlon, the Giants’ senior vice president of communications.

On July 11, Schwartz and his wife, Meredith, welcomed their first child, a son, Alex, into their family. They arrived during training camp and moved into their new house in New Jersey.

“Now that I have a son, it will be extra important to teach him those traditions,’’ Schwartz said. “This will definitely be a good place to raise a Jewish family.’’