I recommend you take your child to a Certified Orofacial Myologist. I didn't know what that was until a few weeks ago.
"What is Orofacial Myology?
Orofacial myofunctional disorders (OMDs) involve behaviors and patterns created by inappropriate muscle function and habits involving the tongue, lips and jaws. They can have a big impact on your health and wellbeing.
The process of correcting such problems is called orofacial rest posture therapy. You may also hear it called “orofacial therapy,” “myofunctional therapy,” “tongue thrust therapy,” “oral myology," “orofacial myology,” or “orofacial dysfunction therapy.” All these terms refer to the same thing."
I have a 10-year-old son & 6-year-old daughter. They don't have that problem. I'll tell you my story. I was told that at age 41 I need braces and FOUR teeth removed. That sounds insane to me. Thankfully I found an orthodontist in my area that can do braces and does not remove teeth out of principle. People travel from all over the US and as far as New Zealand for consultations and work because he is not your typical dentist (and others have had problems surface after typical dental care).
http://facefocused.com/
When teeth are removed, down the road it causes a ton of problems (sleep apnea, snoring, change in facial structure, etc...) Sadly it's still routine. I took my children to see him for a free consultation. He saw that they were open mouth breathers (habit formed to some cleared up allergies) and said they should see this lady
http://www.tonguethrust.com/
When kids breathe with their mouth open, it causes the facial muscles to slack down and causes the jaw to shift backwards (closing in the throat, allowing less oxygen in - which will cause a problem if you decide to become an athlete). She just saw both my kids and said both definitely need it. I can see this. I am astounded that this therapy makes sense and very little parents know about it. I asked her why. She said most dentists don't even know about it. She said that 80% of the population needs it.
There are therapists in your area. There are not many in the US but there are a lot in California. It's pricey and I'm paying out of pocket (subsequent visits will be $70), but that's OK. It's worth it for my kids.