Seriously, I’m at my witts end. My oldest had it down by the time he was 7 or 8.
My youngest, now 12, still doesn’t get it.
A little help please?
Thanks.
At 12, I think I’d start using the opposite sex (if you haven’t already). I would instantly reject a guy who chewed with his mouth open on a date - no questions asked. If you can’t handle one of the simplest, most basic of personal hygiene requirements, I don’t want to know about which other ones you’re neglecting.
How good a shot are you with a squirt gun?
Showing him videos of people doing that on Youtube? I did a search and found some but didn’t review the videos because you’re not paying me.
I’d go with Yllaria on this one.
We struggled with this, too. For the younger child, her teeth/jaw were badly aligned, and orthodontia eventually fixed the problem. With your child being older, I’m guessing that’s not the case, but you may still want to consider whether there’s any chronic breathing/sinus or other physical issue to consider.
Since there probably isn’t, start using peer pressure to your advantage. What are other kids doing? Who’s a pleasure to have a meal with; who’s uncomfortable to be around?
“Lips closed for chewing” was a constant refrain at mealtimes.
Are there other social cues your child needs help noticing?
This.
Kind of a hard question to answer as my child is “moderately” autistic.
I didn’t mention that in the OP because he knows what chew with your mouth closed means.
By moderately autistic I mean: He’s 12 but more or less has the mind of an eight year old. Along with the same academic skills.
Also: Yllaria,Thanks for the best chuckle I’ver had all day.
We worked, literally for YEARS, on getting my son to QUIT SMACKING. He was unaware that he did it, and really felt badly when he was corrected. But he didn’t stop. Trips to stand in the hall did nothing. He was bribed with quarters for a smack-free meal by a former girlfriend of his father’s. Nothing worked until … one day we realized he wasn’t doing it any more.
Can I just say HALLELUJAH???
It was driving us all crazy and we are so grateful that he’s stopped. He’s a good kid and reasonably obedient most of the time. So, I’m no help here; “he’ll outgrow it” is the only thing that ‘worked’ for us. And with your son’s moderate autism, Shakes, I have sinking feeling you’re in for a few more years of it. 
We had my daughter eat with a large mirror placed in front of her so she could actually watch herself as she chewed. It only took a few meals before it was habit. She still forgets occasionally but watching friends who eat with their mouths open helps to reinforce it.
Supposedly my kids have good table manners. (They’re quite a bit younger than yours though - 4, 3 & 1.5) Anyway, I regularly hold contests during dinnertime. The topic varies, but we cycle through Who’s Leaving the Fewest Crumbs?, Who’s ****Holding Their Fork Properly?, Who’s Not Slurping Their Soup, etc etc. Winner gets an extra cookie for dessert, or dibs on the extra dinner roll. Maybe you could start up a friendly rivalry with a sibling?
We also have a nightly contest for Who Did the Best Job Brushing Their Teeth? (Winner gets to rinse & spit first - nice prize huh?) and Who Picked Up Their Toys? (Winner gets their choice of bedtime story)
Shameless & possibly lazy parenting? Yep. Sue me. 
Actually those are really good ideas. I listened to myself during dinner tonight and realized that eating dinner with me must be like sharing a meal with R. Lee Ermey, while he is on duty. “Stop slurping! Wipe your mouth! Quit making such a mess! Where did your pants go?”
Not that I suggest this, but it certainly worked.
When I was little, my very Italian mother and grandmother were flummoxed with my smacking and chewing with my mouth open. They were particularly annoyed that I would talk with my mouth full. So, they’d trick me. They’d wait until I took a bite of food, ask me a question, and as soon as I started to speak, wham on the back of the head. I very quickly became extremely conscious of what I was doing when there was food in my mouth.
In fact, to this day, if someone asks me something while there is food in my mouth, I just can’t bring myself to answer until I’ve swallowed. Which, I mean, is a good thing.
Squirt gun seems like a nicer version of this
I dunno, I made some major inroads with a couple of ADULT friends by very loudly and deliberately smacking my food as obnoxiously as possible while looking straight at them.
They’d be embarassed, then apologize, then I’d say “Sorry dude, but it IS pretty obnoxious”.
Our son’s bug-a-boo was brushing his teeth. No amount of bribery, cajoling, threats, positive reinforcement, or ass kicking helped. I also thought that the whole puberty/opposite sex thing would make a difference. Instead, he just found girls who would be OK with kissing his nasty mouth.
You’ve probably already checked this, but does your son have any issues with hay fever or the like? My younger brother had terrible allergies for years (dust in particular) and his nose was basically non-functional. He wouldn’t sneeze or have itchy eyes or mucus all over his face or anything, he was just so stuffed up that he just gave up breathing through his nose from an early age and walked around with his mouth slightly open all the time. He smacked and chewed with his mouth open because if he closed it, it cut off his air supply. It actually caused his jaw to grow slightly elongated.
It was fixed with an intense regimen of allergy shots. He can now breathe through his nose. Still talks with his mouth full sometimes, but doesn’t chew like that any more.
Of course you’ve probably already considered this, but just a thought, especially since outwardly my brother never had signs of having as bad allergies as he did.
Gah. I’ve mentioned a guy I met from online dating before who had teeth that were practically furry. He could have been my perfect match, and I still wouldn’t have had a second date over that. I guess that guy had to find some woman who wouldn’t mind his fuzzy teeth, too.
For my 12-year-old son, the issue was hunching down over his food, with his mouth practically touching his plate. I nagged. I cajoled. I got exasperated and yelled. Finally, I realized that (like all 12-year-olds) he’s an eating machine. I hit him where it hurts, by sending him away from the table (calmly and quietly) every time I caught him doing this*. He now knows how to eat like a human being.
Your mileage may vary, of course, and this is only barring other complications (like allergies.) The basic formula seems to be Kid + Behavior You Want to Correct = Kid - Favorite Thing. (I’ve also removed computer games, phone privileges, etc.) The only real trick to it is being consistent in enforcement until the good behavior becomes a habit.
*Being sent away from the table meant that his meal was over, and there would be no snack or dessert or whatever to tide him over until the next meal. Like most American kids, he’s in no danger of starving.
Ah yes, LM. This is what we call eating “prison style” - luckily my kids are ok when I say “sit up and put your back to the chair” so that they will be basically forced into better posture and have to bring their forks to their mouths. It is interesting. I know we all know it intellectually, but sometimes I wonder if my kids are the only ones that do these things sometimes. I once looked at someone and said “I promise they didn’t learn that at home” when it was a combination of slurping, prison-style eating, and making fart noises at the table. Tonight when I was going through the list of how to have good manners and what was gross my beloved smart-ass 9 year old looked at me and said “Mom, you just need to respect the boy-ness of the atmosphere here.”
God help me, I’m outnumbered and it’s a frat house free for all sometimes.
My son used to chew with his mouth open. I don’t think he even realized he was doing it because if we pointed it out he’d make a conscious effort not to do it.
Anyway, after one warning to stop, we explained to him that it is unpleasant to eat with him if he can’t chew properly and then left him to eat alone. We only had to do that twice and I think we’ve only had to remind him once or twice since then.
Oh, he’s seven now but this all happened last year.
Is that what it’s called ShelliBean? I just refer to the eldest as a feral child. And at our house, it’s the 9-year-old girl who’s most likely to laugh about all things gaseous at the dinner table. (Maybe it’s the age?) It can be a little disconcerting, though, to see little miss prim and proper, with her nails painted and her hair “just so,” crying with laughter about farts. I’m no longer outnumbered (although the 8-week-old is only up to eating, sleeping, pooping, making funny fart noises, and joyfully rediscovering her hands and feet each day. She’s not a civilizing influence yet.) But it’s still like a frat house some days.