Hi there and welcome! I read your post and thought, oh wow, poor boy! Many of us here have adopted kids and it sure does add a dimension to things. I have (and many here have) lived through the calls every day. My son is only now at a school in the last couple of months were that is not happening.
If your son has those diagnoses, I suspect, just MHO that he does have issues that extend outside of school BUT what he has going for him, (and I believe with all my heart our adopted kids are just as planned to be OURS and any child born into a family...for the better or the worst)...he has YOU. You get him and have him in activities that match his needs. You sound like you are a person who gets his style. Given his background, it would be hard for any kid to really internally think that people can fully be trusted, right? (again this is my opinion...my son did not have a terrible background but did have a change of caregivers twice at an early age and was in pain for a large part of his very early childhood)...As a teacher you know that the basis of our core personalities is created in the birth through age 3to4 years. It takes a very structured yet SECURE, I wont give up on you, you are valuable, kind of setting to help overcome that. (and there are some who just dont, even when parents do everything they can..but your son is young).
It seems like there are so many issues here that can be making what is a very challenging situation difficult. First, your school is wrong and if you get an advocate to help...this might be turned around. There are many many many kids on IEP's who do well academically but can't function well in the classroom so have to be on IEP's. IF behavior impedes their progress OR THE LEARNING of others, they needs support. Social skills are absolutely considered in special education (you probably see that yourself in teaching, are you in a public school??) If you look on Writeslaw.com you can search behavior and you will see how it is worded so they can't deny he needs support. Kids in EBD (emotional/behavioral disorder programs) and Autism Spectrum Disorders (ASD) programs and PI (Physical impairment) programs often do great academically, but they needs support to function in all aspects of school.
Secondly, being the minority is a factor. My son's new school has teachers that look like him (he is mixed Hispanic/African American) and students that look like him and he really needs that connection much more than I give credit for because he has so many other issues so it is often a lower consideration. But, even though he isn't culturally being raised in an Hispanic/AA setting, it clearly makes a huge difference to him, I am so happy for him. With kids with complicated histories and issues, many little things can add up and we often have to tick through many issues to start to get a handle on things.
If a child already has a history of solving things on his own and not getting proper guidance, of course they are going to need a long time to help learn how to accept that people telling him what to do and getting along with others is the way to get ahead. Here is the attach-China website
http://attach-china.org/ which I really like (they also have a yahoo support group much like this where parents talk about their adopted kids)...it was started by parents who adopted from China but is a site for people who have adopted kids from any country and even if not adopted, children who might fall on the spectrum of Attachment Disorders. Some of the things you mention, his being able to be sweet and charming in some settings and falling apart do fit, but his being great at home and struggling at school is a little different pattern for many (though on that site there are some like that, the kids who are insecure and really need to be with their moms alot and need small comfortable places to learn). Many kids do not have full blown Reactive Attachment Disorder (RAD) but have serious issues with trust ranging from being overly trusting and will glom on to anyone--to not being able to trust anyone even the person that loves them the most. This site has families who really have had a lot of success in this specialized field of therapy. Even the most well meaning therapist can really screw things up for us if they do not have specific training and practice working with kids who have attachment challenges.
The other thing that I was wondering....many kids from this kind of setting have a couple of risks....one is alcohol and drug exposure during pregnancy and one is that they have sensory integration disorder (and many have both). This may not apply at all, but sometimes we just dont know and have to investigate because adoption records may not be complete. Kids with fetal alcohol spectrum (from "effects" to the full syndrome) often have behaviors that look like rage and anger. They just can't modulate it well. Well, they often can't modulate a lot of things well. They often can not do well socially, esp. with peers in groups. And if sensory things are involved well.....if I felt like someone was scratching me or poking me or screaming in my ears all day I'd be pretty darn crabby too (every child is different in how they feel, some as you likely know...dont feel things as much so seek out loud, touch, banging, throwing etc.).
Given his style of learning...(from the settings/activities you describe where he is doing well) he does well in highly structured, clear expectations, low teacher/child ration setting, do I understand right? ...it seems your gut is telling you that this kind of school is not a good placement. It could be that a private school IF they have a lower class ratio and can give individual attention might work. However, they do NOT have the obligation to work with you if he does have special emotional and behavioral needs. They can suspend as much as they want to and do not have to evaluate or consider your private evaluations. I am sure you have thought of this but you may want to go in when you look with a list of questions and ask for parents to talk to so you can play dumb and ask what they have seen happen with kids who have behavior issues or bully etc. (not saying your son is a bully, trying to find out how they handle kids). If they say there are NONE..RUN. That likely means they remove them so that their school is not disrupted. There are always kids who struggle. The kind of behavior modification your current school uses...(I am saying modification sarcastically) just gives our kids a day off, punishes parents, and often reinforces their low or "bad" self esteem. The law says that they must (in special education) use a POSITIVE behavioral intervention plan. This is common sense for any child. And it goes beyond rewards and consequences....it means setting up the environment for the child to succeed. If you decide to stay in the public system, even if you switch schools, I would in writing request an evaluation so they have to put in writing why they deny it (if they dare to given his high frequency of calls home and suspensions, they have dug their own grave). Once you get past that since you put it in writing, they have time limits to get things done. That is federal law so no getting around it. It is well worth the fight, but sure is exhausting.
Sounds like you need to borrow our warrior mom armor. I have had several suits shared with me over the past year especially! Just MHO, but I would get a private neuropsychologist evaluation to get a better handle on what is really going on with him, (a long.....not just a psychiatric test or psychiatrist meeting...evaluation...). A neuropsychologist looks at behavior and helps create a profile of how our brains work related to behavior, they give a much broader view of whether things are neurologically based versus or along with emotional/behavioral issues. They can help describe learning style and needs and if he is gifted but with special challenges they can help give recommendations for settings and ideas for what to do in the school and private therapy arenas. Schools MUST consider all private testing (again mandated) but do not have to blindly accept results. (makes it clear as mud) Looking at what you have written, I'd probably an Occupational Therapist (OT) evaluation too. He may get overly stimulated in a setting like that. They can examine if there is anything they can do to modify the school setting that really is not a big deal (offer head phones, sit on a ball, etc.) but they wont think of it unless someone (other than mom) points it out.
Finally with his intelligence level, well, even if a child has special needs, they also can have typical reactions and so again, adding another layer of what often happens with gifted kids....yikes! This kid is really lucky to have you!!! He seems really complicated.
I am single and had to quit my job but had the option to be paid through my son's insurance at a PCA rate to care for him. Most dont have that, plus given your difficult child's needs, it could be very intense to have him be home-schooled. You are doing well with him so if it was me, unless there were no options I would not throw that complication into the mix and risk an issue, lol. Lots of folks here do it though and do it well.
Well, I have babbled enough. Welcome so very much to this amazing group of people. I hope you find what I have, that this is one place where we can make mistakes, cry, complain, hate and love our kids at the same time and still be considered and supported!
EDIT: darn I know I should shut up...sorry. I just looked down at my copy of LOST IN SCHOOL by Ross Greene and thought you might really be interested. It could help you sort through how to present what your son needs and why suspensions/consequence based methods do not really work for him. It is by Ross Greene. EXCELLENT book (he writes The Explosive Child, and you might like that too...as your son gets older and teen years hit, could be good to start now, LOL)