The physical form of Humans are built upon genes/DNA, akin to mechanical parts of a robot, except it is biological than mechanical. It is the gift of spirit or life force that OPERATES the parts of the Human body. Imagine a saloon car which is a mechanical robot, can it operates as a tractor? It can't, as it does not have the necessary parts to be a tractor.
Thus, Homosexuality is an IDEOLOGY, not biology. There are parts of the Human body which are different, & of different use among the 2 genders. The spirit/life force is akin to the driver of a saloon car who operates it, in the fashion that the saloon car was meant to be operated & will not function as a tractor. In order to battle with ideology, it will take a BETTER IDEOLOGY to overcome an ill-conceived ideology, the way Humanity fought & won against radical terrorism, as NO bullets or physical means can destroy such ideology. The battle lays in one's mind.
There are many good counsellors whom may be able to help the 12yr old teen. At such age, they are vulnerable & subject to all kinds of changes, physical & mental, in their critical formative years. Rather than despair, the parents must get to the root of the issue - why that change happened as Humans of all ages can only be motivated by reason - the mental process that led to their actions. It could be a number of causes - peer pressure from an all female environment, an escape from loneliness & lack of popularity, a desire for the lovely form of dresses onto the Human body-a designer in the making, etc.
Upon finding the reason, gentle persuasion & guidance into the practices of males will do better than physical harm, as kids at their age will be rebellious as they will realize that life is no fantasy-of santa clauses or fairies, etc, that they had been lied to by their parents, & will listen/trust their peers more. Thus a need to rebuild that trust, guide & mould the child to his designated path to live life & contribute to civilization.