A locked unit doesn't mean the patients and staff will be protected.
Most ped psych inpatient units have very well trained staff who deal with aggressive behavior all the time.
But not with sexual predators.
But that said, I suppose the teen could be placed in a locked room, with 24 hour supervision and cameras.
Male nurses and aides, or females only go in with a male aide.
It would requite additional staffing, which the hospitals hate to do.
But I suppose it could be done. Huge liability for the hospital however.
And the kid would not get the specialized treatment he needs.
There are juvi detention centers with psych staff, but I am not sure they would be able to deal with this kind of situation.
I am aware of residential treatment centers which specifically treat sexual offenders, and this is probably the best place for this child.
But it all depends upon the initial evaluation, for example, residential won't take someone acutely psychotic most likely. In that case he would have to
be staged in various clinical settings.