Well I imagine it's fairly less distracting for other students since it's way less obvious and out in the open.

Well that's a lie, as chewing on things has been one of the best focus aids for my ADHD for about 30+ years.

I have ADHD. Have had it for all 40 years of my life. If I do NOT have something to fiddle with then I am not focusing on ANYTHING. If you try to force my to pay attention to you while talking to me, I will not remember a damn thing you said no matter how often you said it. But if I have, say, a spoon to nibble on or a pen to twirl or even just a ball to pass between my hands it will distract the part of my brain that NEEDS stimulation and let me concentrate enough to listen and memorize what's being said to me.

And, yes, I use chewing gum to help with this as well...since the chewing action satisfies that need for stimulus.