I have significant ADHD so this is the story of my life, even when on high doses of meds. I am also a teacher, so feel free to PM me with more questions if you have any!

When I have to sit for an extended time, I benefit from having a physical therapy elastic (basically a strip of GIANT rubber band) tied around the front legs of my chair. I can rest my feet on it and bounce my legs, or kick it by alternating my feet, or place my feet behind it and press forward with my ankles. It basically lets me get movement with all of my leg muscles, glutes, and core while staying seated. *edit: this can also work using the front legs of a desk or table if your legs are too long for it to be comfortable on the chair.

There are also wobble seats available on Amazon for under $15 (other retailers as well, Amazon is just an easy go to for demonstration): https://www.amazon.com/AppleRound-Stability-Cushion-Diameter-Included/dp/B007LX6MPG/ref=mp_s_a_1_12?dchild=1&keywords=wobble+seat&qid=1594472470&sr=8-12 You can increase and decrease the inflation until you find the right tension place for it to force you to use your core muscles, which I find to be a good way to keep the bored half of my brain occupied while the focused half continues to work.

I give myself and some kids brain breaks with a timer. Even if they are focused and don’t want to get up, many benefit from forcing themselves to stand up every 30 minutes to do squats or planks, and then get back to it. It helps their mind stay calm knowing a break is coming, in the same way that our circadian rhythm helps our bodies stave off hunger while we’re asleep. Other options are playing a song and dancing your heart out then sitting back down as soon as it ends, or leaning against a wall in a push-up position while reciting an affirmation.

It can sound kinda hokey when an NT makes suggestions to me, but I’m ND as hell so these are coming from personal experience as well as professional expertise. :)