In my experience, students often start to exhibit signs of gender dysphoria at puberty, at an age when they’ve become capable of reflecting on the subject, but before they’ve fully developed as sexual beings.
The teenage years are a period of transitional unease and uncertainty for everyone, as our bodies and brains experience profound changes in both personality and sexuality. We start to become different people from those we were as children. New and intoxicating hormones and over-production of neurotransmitters buzz up our brains. Imbalances trigger storms of emotion that we seem to have no control of. The calmest of children become volatile to the point of hysteria.
This will cause existential angst in the calmest most grounded of us, and we become obsessed with self-definition: pinning ourselves down, firming up our identities. It’s an anxiety-inducing turmoil.