“One of the things we tell students is they shouldn’t steal the neon-colored cloth napkins and stick them on their heads like bandannas,” Mr. Jasgur said. “For every napkin that isn’t there at the end of the night, Johnny’s family is going to be charged. It’s $4, $4, $4, and all of a sudden it’s a lot of money.”

Instructors also talk about grooming. Boys have to be told to hike up their sagging trousers and not show off their boxers. Girls have to be told to pull down their shrinking dresses and not reveal inappropriate amounts of skin, and they are also encouraged to sit with their knees together and ankles crossed.

Last year, after a deluge of rabbis asked if they could visit the classes to warn students about their behavior, Mr. Jasgur introduced a one-hour course called Mitzvah Circuit 101, which he offers free to synagogues and Jewish community centers. The course includes a questionnaire about the proper way to respond to an invitation and what to do during the video montage. The following question addresses what Mr. Jasgur says is a common sore point for parents — students dismantling the centerpieces:

On your table you discover the following: ketchup, sugar, water, a movie-themed centerpiece and a bowl of mini chocolate Academy Awards. Do you a) quickly remove the two DVDs from the centerpiece and claim them as your own; b) take the glass of water, add two parts ketchup, three spoonfuls of sugar, four Academy Awards, and see if Mickey will drink it; c) arm yourself with the mini chocolates and see if you can hit Jason at Table 5 without his knowing where it’s coming from; or d) none of the above?

Why the need for the new course after so many years? “Should we blame it on society? Should we blame it on parents? I’m not sure,” Mr. Jasgur said. “Today’s kids are just overprogrammed. Their focus isn’t there. Many of their parents are also part of this younger generation, so it’s not their fault. It’s the way they were raised.”

Rabbi Adam Englander, a principal at the Hillel Day School of Boca Raton in Florida, lectures students three or four times a year about their behavior at bar and bat mitzvahs. He believes the new interest in decorum represents a larger shift in society.

“In my opinion, I don’t see it as a function of kids being poorly mannered,” he said. “I see it more as a function of schools being involved in much more than education. Schools are increasingly being asked to take on roles that years ago would have been considered the realm of parents.”