My study of this in the 60's had and continues to have a positive effect on my life. Books like I'm OK You're OK were a part of it. https://businessjargons.com/ego-states.html
I went through that program in the 1960s also, using the "I'm OK, You're OK" book. I volunteered for a crisis hotline during my junior and senior year of high school, and that was a part of the training, although I couldn't see what it had to do with anything. During the same period, I read "Games People Play." As I remember, the TA guy recommended it. I'll probably start a thread about my crisis center experiences in a day or two, as long as my wife promises not to read it. When you're dealing with a life crisis or contemplating suicide, there's nothing better than calling a crisis hotline and talking to a couple of 14-year-olds who are there for you, largely because it gave them an excuse to spend the night together away from home. It's probably even more useful when the kid on the other end of the phone is on acid. As for transactional analysis, my 14-year-old mind did try to make some sense out of it. I actually read the book and attended all of the classes, but I thought it was kind of goofy at the time. I haven't given it a shot as an adult, however. I suspected it was a cult thing.
The OP is about: "Transactional Analysis And The 3 Ego States--parent / Adult / Child." I have been there in all three states, and done them, but in this succession: child / adult / parent (+spouse), in addition, / widower, and now, / moriturus. Funny, I am so far the third contributor to the life history (Oct 20, 2019 - Feb 17, 2020) of this OP, what's wrong with the OP?
I expect that most of the people here have never heard of transactional analysis, or don't know enough about it to contribute to the discussion. Plus, the originator of the thread hasn't been back to it. Generally, the thread originator moves a thread along.
Let's see what I remember. TA is a bit more complex than just 3 states of child / adult / parent, and there are a variety of versions of the model. The way I learned it, each state has two modes: wounded child / natural child adapted adult / authentic adult critical parent / nurturing parent We can be in or be acting / responding from any of these states at anytime regardless of age. These states are basically a way of becoming aware of our patterns of behavior and what motivates that behavior. I found the model useful in counseling clients, and to an extent, also useful in understanding the dynamics in corporate cultures.
I actually thought the world had moved on from this concept. I was taught about it in the mid-70s along with stuff on biofeedback (same teacher). I respected the instructor greatly, but got nothing from her stuff on TA.
Wow! the mention of TA and the cobwebs of my mind started swirling! Nope. Can't grab onto any of the debris to talk about it intelligently but I did one of my majors in psychology. It brings me to another thought, though. When my youngest was in public grade/high school she was put into a mediation class where the kids were exposed to the concepts of mediation. I believe the thought was that kids could calm a situation better than adults, if given the tools. My daughter was/is very shy so did not use the tools. But I did think that teaching small groups how to talk to each other without bullying, teasing, etc would be a great skill to teach. Lots of kids, if feeling uncomfortable in verbal communication might resort to less civilized forms. Maybe teach "How to Make Friends and Influence People" would be a better course than CRT. Teach; Learn and Respect other people Maybe a forum like this one for kids since the Department of Education is worthless and will never do this.
I would not completely discount this theory. It has been useful in my career in dealing with subordinates and with bosses. I think it applies in interactions with authority. Perhaps the degree to which we embrace this says as much about ourselves as it does the validity of the theory. And this brings to mind the brief era of John Bradshaw. Or is he still a "thing" in certain circles?
At first I read mediation as meditation, which I hear in some schools is having a similar result -- less bullying, less conflict. Either way, both are quite useful and in my opinion should be taught along with the other basics, including our unvarnished history, all of it, all sides, good bad and ugly. Good question, and I don't know. It was big when I was getting my masters and I used his work with individual clients, and with non-profits that behaved like ACOAs.