Today gender is being redefined as a choice but that's a little like saying Gay People are "normal". Both are distorted interpretations of existing words intentionally misused by people with agendas.
Normal has always had it's roots in statistics and never included anything unusual including geniuses, super athletes, straight A students, or even Gay People because the majority of the population doesn't have those traits. Similarly the nouns boy and girl have always been in alignment with male and female genders which in Humans never changes.
Today we are telling children that they might have been born with the wrong genitalia and if so that can be fixed. Children in elementary school learn about men who have become women and women who have become men. I see lots of problems as a result but one thing is certain, at least at this time, no one can become male or female if they weren't' born that way because both are defined by their REPRODUCTIVE equipment. Yes, I know that it's not PC to utter that fact but it's true.
There are many animals that transition from male to female or female to male, but ALL are defined as male or female by the reproductive equipment they have at the time they are being categorized. In animals that produce sexually, the female sex ALWAYS provides the egg and the male the sperm, there are no exceptions. That categorization has always applied even to sterile organisms.
Telling children they can choose is wrong because even if they want to it's physically impossible. The best they can do is assume the physical appearance and pretend. Perhaps that's why the highest suicide rates are among Transsexual people who swallow all the PC propaganda, spend tens of thousands of dollars for therapy and surgery, only to find out they are often worse off than they were before they did all that.