I don't know for sure whether your BF is his perp's only victim. But, I do know what I believe. And, I believe that he probably has MANY other victims. Perps, expecially teachers, coaches, boy scout leaders, priests, pediatricians, etc, almost always victimize many children. It's like these professions that have access to kids are magnets for perps. In fact, I believe many perps choose such careers precisely for such access to target their victims.
I remember telling my story to a police detective. Though I never forgot what happened to me (I just never told a soul for 18 years until I told my wife and then the detective the very next day.), I never realized how much effort and planning my perp put into abusing me. When I finished telling the detective everything, I looked at him and said, "He set me up, didn't he?" He then said to me, "We call it grooming." That was the first time I heard that term. Realizing for the first time how my innocence had been taken advantage of and the lenghts my perp went to get my trust was very traumatic for me. It multiplied my rage because I knew he just didn't take advantage of a situation. What he did was very deliberate. It took a lot of planning and then execution and, as is all too often the case, the willingness of other adults to turn a blind eye to what was going on.
That was another part that was very difficult to accept, and it's still hard to think about that today.
So, for your BF to be getting help is commendable. So is reporting his perp to the folks responsible for his teaching license. I hope they take him seriously and do something about it. Your support for your BF during this time is also very commendable.
Take care of each other,