I think that, because of the way their lives were, Yelena, Ava, and Bob don't have their GEDs.
Yelena because she was stuck into the Red Room at age 6 (if I remember correctly). Ava because she's been used by SHIELD since her father's impromptu lab blew up and her body started falling apart. And Bob because he dropped out of school somewhere between 7th and 8th grade (if i remember correctly).
Now that the Thunderbolts are all together, and they're not really on the run, or in poor living conditions, AND they have (possibly) a good, stable income, I think they start working on getting their GEDs. I'd like to think John encourages them when he finds out they don't have their GEDs/high school diplomas.
John also probably has a college degree, along with his high school diploma, because the military usually makes its members take college classes while their in the military. I'm not sure what he'd have a degree in, maybe something basic.
But anyway. John one-hundred percent helps Yelena, Ava, and Bob with their studies at the dinner table. Cue dad helping his kids with math. And also Bucky uses this as an opportunity to learn modern-day math, science, history, and english.
Speaking of Bucky, he has every Thunderbolt (Alexei included) enrolled in "Bucky-mandated therapy" as they call it. Except they all have good therapists that aren't passive-aggressive and actually work with the Thunderbolts to get better.
Getting back on track, when Yelena, Ava, and Bob get their GEDs, John takes them out to a nice dinner to celebrate and tells them that he's very proud.
Also, if any of them want to get a college degree, John would be very supportive with that too. I'm not sure what Yelena would get, but I can see Ava being interested in quantum physics and Bob being interested in social work. For Bob, specifically, in children in troubled homes, but he would also definitely be a little too sensitive to deal with it firsthand. For now, at least.
saw a post on twitter about bob and his amnesia after being void/sentry and I have a headcannon.
my headcannon is that bob remembers everything about being sentry. cause that’s like his highest mood ever and he’s so happy and having a good time. except with valentina, obviously. I think he was like a mix of bob and sentry.
he also forgets about being by void. since that’s like his low time where he’s sad and depressed.
it’s a bit self indulgent for me, cause I remember everything from when I was happy. like hanging out with friends or going to a concert. but I don’t remember my family trip to universal studios like at all cause I was so depressed
like starting drugs at such an influential age (like 13yr old) definitely altered bob's brain structure. now that he's off meth/possibly other drugs, it almost feels like something's missing, I'm sure. he definitely, unintentionally, gets addicted to other things while with the Thunderbolts.
but being addicted to something isn't always bad.
I mean, you can be addicted to working out. it's definitely a thing i've witnessed happening with a family member of mine. so I definitely have some outsider experience with an addictive personality