This is a very good question, and I hope I can do it justice.
When I was thinking of opening a high school seminary I asked an archbishop his opinion and he gave me this unexpected answer (everyone seemed to be closing their high school seminaries at the time). He said, "I went to a high school seminary myself and I don't regret it one bit, I may never have gotten to be a priest otherwise. High school seminaries when I was young were good things, today I think they are absolutely necessary!" He then went on to speak about his concern with the trend towards older vocations that was taking place at the time, "We don't get to know them well, there are things many don't seem to grasp, many come with baggage they could do without."
There are three elements or levels to take into account when speaking about high school seminaries. One is the viability and desirability of high school seminaries in the abstract (i.e: should there even be high school seminaries?), the second is the nature of a particular high school seminary (how this seminary is run, the level of formation there, the atmosphere, the order and discipline, the spiritual life... These are usually reflected in the boys that are studying there: if they are safe, happy and love our Lord) and the third is the individual boy (high school seminaries in the abstract might be a good idea, but is it a good idea for this particular boy to go to a high school seminary?)
I will run briefly through each one.
Recent Church documents, from Vatican II to the document on priestly formation called "Pastores Dabo Vobis", have all spoken positively about the place and role of high school seminaries in the cultivation of vocations and the formation of priests. The Church has always taught that some young people are called from an early age to give their lives to God, and they should be helped to do so. The question of being physically separated from the family has never been a major concern as long as there is a healthy communication and interaction, which today through email, telephone/skype and the ease of travel is more possible than in the past. Each school of course will have its own concrete policies and nuances. The question of psychosexual development, and possible moral dangers are more a question of the way a particular seminary is run, and not of high school seminaries in general, and also of the individual boy.
If a particular high school seminary lives up to what the Church has in mind when it speaks of high school seminaries, is something you or your husband will have to verify personally. Visit the school and see for yourself if the atmosphere in general is healthy, if the boys are happy and respectful, if the discipline is positive, and if the boys are busy. Speak to the teachers, speak to the formators, speak to other parents. See if groups of boys can visit, and if their fathers can go with them to have the opportunity to see everything on the inside over a period of days. Check out what prayer life is encouraged, what responsibilities the boys are given, if their life is balanced, if they play, if a sacramental life is encouraged, if there is devotion to Mary, if there is a spirit of charity and friendship among them, if there is self-mastery and high expectations, if there is love for the Church and for souls, if the atmosphere is one of joy.
Thirdly, you have to remember that even though high school seminaries are good in themselves, they may not be for every boy who is interested in the priesthood. The parents are an integral and necessary part of any decision in this regard, because of the boy's age. Parents are in the very delicate position of having to make a prudent decision as regards what is best for their son's vocation, so if they decide against the high school seminary it ought to be for reasons that are not selfish, and it ought to be in the best interest of his vocation. If a boy expresses an inclination to the priesthood at a young age and the parents for whatever reason decide against the high school seminary, they ought nevertheless to be conscious of the possibility of a vocation and resolve to do all they can to help and protect whatever vocation there may be there. It has been my unfortunate experience in many cases to see that parents out of misguided zeal for their sons to have "normal experiences" tend to push them into situations that prove destructive for their basic Christian life, not to mention a possible vocation. Kids are always going to have friends and do things together, coming under each other's influence, so when choosing for your son it is good to be very realistic about the atmosphere and circle of friends he is going to be immersed in either place, and the influences he will be under.
You may have further questions, but just to summarize: the Church is in favor of high school seminaries, you have to check out the individual school to see if it is well run, and to judge if it is the best for your child. The best way is to visit and speak to parents of other boys at the school. And if you are open to your boy going and he wants to, don't let him jump right into it, make sure he visits there and participates and does an introductory program so that the formators at the school have a chance to get to know him, see him in action and say if they think it is the place for him.