Sadly I don't think there are many GPs who would even look for gut fermentation let alone test for it.
I feel this is a crying shame as am certain gut fermentation is far more prevalent than is known about.
i am convinced lots of kids could have their behavioural and/or learning issues 'fixed' if this was looked at.
Come on GPs, get it on your radar!
If you do feel some symptoms are same as my DD, but not all, it's worth bearing in mind that different people can display different symptoms.
If you think about how different adults can behave when drunk - some become aggressive, some are away with the fairies, some are merry and amusing, some morose, some wild and untamed, some dont sleep well (certainly not restorative sleep), some might also experience subsequent probs such as constipation or diarrhoea, some might have a variety of different behaviours or go through a spectrum. Looking at the variety of effects that alcohol can have on an adult body it's easy to understand how a child might be affected in numerous ways if they are fermenting foods in their gut.
You could do a mini trial to see if you notice any changes by cutting out sugar and yeast for two or three weeks. These are the main culprits and although there's a bit more to it if clearing out yeast/bacteria, it might be a good starting point for your own peace of mind to see what link you do or don't find.
Sugars include fresh fruits so they need to be out of bounds - but you can keep pineapple, mango, kiwi, papaya, melon, blueberries and green apples as these apparently ferment less, just keep a check on how much per day in order to avoid lots of sugar sneaking in - one or two portion and no more, but then that's in line with what we should be keeping it to anyway so that's not a crazy plan by any means. Cutting out sugar also means dried fruit, fruit juice etc and anything that it is an ingredient in - for instance lots of breakfast cereals, lots of sausages contain sugar (good little sausage company is ok as no sugar), some bacon brands have sugar in. Just need to have a blast of serious label reading and plan ahead for a few days at a time. The sugar in cows milk is also not great so switching to oat milk or goat milk for the two weeks would be useful too. (Ditto use goat butter and goat cheese). White potatoes best kept in check aswell as v starchy and they turn to sugar quickly. Don't have everyday and certainly not more than once a day. Sweet potatoes are ok.
On the yeast front, the obvious thing to cutout during mini trial is bread. Also other things such as use gluten free pasta instead of regular.
Sounds heavy going but is ok if you can make a list and plan. Just need to become an ingredients-reading addict! Fresh veg, meat, fish, eggs all fine. There really is plenty you can still have. I am about to cook the full Sunday roast chicken malarkey and the only thing I am changing is no stock cubes as most have yeast in - but I suppose I should be making gravy with juices anyway so it just makes me kee it fresher. Means you end up have a v healthy diet! Oh yes, meant to add, really helps if everyone does it together as is v supportive and also makes life easier for the cook.
Keep a daily note of what happens/behaviour, mood, bodily functions, learning, concentration, memory, focus. etc
For a two week pain in the behind it could be a major gain 
The other thing that comes to mind is the whole sleep issue. I recall reading an article in new scientist ( a few years back so I can't get my hands on it at the mo) that said most common misdiagnosis of ADHD was actually sleep apnoea. Any sleep disturbance, or lack of sleep, commonly manifests as symptoms that can be mislabelled as ADD. By the same note, gut fermentation also affects sleep and makes it less refreshing sleep, threfore can have same 'ADD' effect.
Soz for long post!! Thought best to explain a bit more detail in case of use as this info seems to be sadly lacking from many of the usual routes. Am very fortunate to have a health professional DH who knows his onions....!