You don't provide enough detail about your step son to understand what you mean by 'emotionally fragile' and what sort of 'trouble' he is getting into.
Step parents searching for boarding facilties is a hot button for many here, including myself. Why isn't his father conducting the search? Why is boarding being considered?
I know of no Therapeutic Facility that will help him "unlock all of the amazing potential that we believe is inside of him." That requires a respectful attitude toward the teen and support in the direction of their passion and goals- car mechanic or rocket scientist.
The lessor of the evils would be a traditional boarding school. One example is Putney School.
http://www.putney.com/There are probably academic requirements which your step son may not meet, depending on his situation and the school's requirements.
Note: I am not recommending or endorseing Putney. I just happen to know a young woman who went there, not due to 'behavioral' issues, but because her parents were "too busy" to parent. Her father was wealthy and was sent to a boarding school (military) by his parents. Other than being away from her family, and all that entails, she enjoyed it. It appears to be a decent school, as boarding schools go. I think they sufficiently engage the teens so the loss of connection with their families is not so dramatic.
I know seven kids who were sent to religious, therapeutic, or wilderness programs; and none have happy endings. They were not offered the type of environment and opportunities that Putney offers. In fact, it was more like being in prison, behavior modification prison. None blossomed. All resented the experience. One died while at wilderness. Two were sexually molested. One (for certain) left with PTSD. One lost his joy and enthusiasm. One ran and was raped by a truck driver- which she said was less stressful than the facility!! Steer clear!!
If I were in your situation, I would try to assess what the underlying issue is.
Is he bored? Angry? With whom? Confused? Overwhelmed? Sad? Hopeless?
Whatever the issue, respect is always called for.
Ask him what his goals are for himself and how you can assist him in acheiving them.
Engage him in finding the 'solution'. It's disrespectful to make these decisions without their involvement. Period.
It might go something like this:
It's obvious you're not doing well in public school. I don't have a solution for you but would like to help you figure out how to meet your goals for yourself in terms of education. I will give you my full support in that direction.
Shall we start by looking at alternatives for finishing high school?
Responsive- great! Go with it and then support him fully.
Non-Responsive- time to deal with hopelessness and possibly confusion.
Put education aside for a short time and address those issues in a positive way.
Example:
What are your short term goals and plans for yourself? Long term?
What sort of lifestyle do you desire?
Let's run a budget so you can get an idea of how much money you'll need to earn in order to support that lifestyle. Do a good job with this- make it fun, letting him do as much of the research as possible to 'educate himself' about the realities of the cost of living.
Now, what are your passions? What work would you be excited to do everyday?
Don't know? Shall we go to a career counselor at the local community college? They have massive volumes of books with every job you can imagine. They can also help you identify your strongest attributes and help narrow the choices.
Determine the education required. And ask where/how he might like to receive that education.
This is not done as punishment. It is done to rekindle the fire inside him. To reinstill hope. To clear away some of the confusion and fear that most teens deal (or not) with. To let him know that your ONLY agenda is to help him further HIS goals. And if he has none, help him remember that he does have goals. They're just temporarily out of reach due to hopelessness or 'fill in the blank'.
And, your relationship may be so damaged that he won't trust you enough to engage in this way.
Then, I'd say it's time to really put education on the back burner and heal the relationship. Find a tutor to work with him. Take him to work with you. Hang out and do more listening than talking. Take a l-o-n-g educational vaction. If you find yourself lecturing (out of fear for his future) SHUT YOURSELF UP and listen. Listening is about the only thing you can do to foster genuine trust. If you were down and out would you want your friend or spouse to lecture and or threaten or banish you from their lives?
Treat him with the respect he deserves.
If his behaviors threaten his freedom- Take him to a teen prison. Let him see the realities of the world he may have to deal with if he makes the 'wrong' choices. This is not abusive, it is very important that teens be educated on reality- the police state they live in. There will most likely be no 'rehab' if the state were to gain custody. Only jail time. Does he understand what behaviors could cause the state to gain custody? How that would impact his life? Would he be okay with that? Would he like to avoid it? Does he know what a felony is, or a misdemenor? Or the difference between the two?
What you should know is that many, if not most, kids have 'trouble' with public schools. I think I read that only 25% (or less) 'do well'. The average teen has at least 3 encounters with 'the law' before they're 18. If you're feeling stressed and worried, look for the facts to help dispell your exaggerated fears. He will not open up to you if he senses you have an agenda that is motivated by fear. Consider yourself in service to his education about living in this society.
I'm wondering why you feel like you need to send him away. There's always:
Homeschooling (with the aid of a tutor if necessary), Alternative High Schools, Trade Schools, etc. Education is ALWAYS available, no matter the age. Let go of how it should look or happen.
For my own son, who returned home from a military academy with PTSD, I found a wonderful alternative high school (after he'd been kicked out of public school for smoking pot).
http://www.griffinschool.org/This school was perfect for him. A stimulating refuge from the mundane, sterile environment of public school. (Don't freak out at some of the pictures of the kids- they were some of the most intelligent, creative, independent thinking teens I'd ever encountered- just square pegs that couldn't be forced into the round holes in public school. And yes, the majority smoked pot.) Example: One 16 year old female had her own apartment, worked to support herself and pay her adjusted tuition.
He most appreciated that the teachers didn't patronize. They genuinely cared, and teens/kids know the difference. There was lively, passionate debate daily. Subject were taught with passion and from many perspectives. His History teacher even used Howard Zinn's "The People's History of the US" for a text. No one's voice was squashed. Teachers went by first names. There were no 'disciplinary punishments'. If a student was not doing well a meeting was called to discuss what was going on for them, to re-examine their stated educational goals and the commitment they had made to themselves and the school, and to brainstorm how teachers and parents could support them in achieving THEIR goals. The adults should have NO goals for the teen that s/he did not participate in creating.
Point being, there are usually more resources locally than one can imagine. Shift the direction of you search. Shift your thinking about your step son. Imagine if you can, the fear, confusion, uncertainty that teens attempt to deal with on their own. Particularly those who don't do well in the public system.
Parents should make a vow to their children when they're born, much like, and with all the sincerity that one might make a marriage vow. If not publically, then privately. In sickness and in health, in ease and in distress, in confusion and in clarity, in anger and in joy, (I could go on); I will love, honor, respect, and cherish you til death do us part.... It should be read frequently.
Can you, as a step make that kind of commitment to him? Can his father? Someone should. And it will not be a boarding facilty, even the best, high-dollar traditional school.
Whatever happens with your step son, I hope someone along his path helps him master his environment and make it work for him, instead of against him.
That's my two cents worth, for what it's worth.