Hi jorgezamparini
Yes, you can buy him the Half Fare Card for Youth, starting from his 16th birthday: https://www.sbb.ch/en/travelcards-and-tickets/railpasses/half-fare-travelcard.html
In addition, if he travels a lot at night, you might want to check the Seven25 offer (it is also available with the Half Fare Card): https://www.sbb.ch/en/travelcards-and-tickets/railpasses/seven25-travelcard.html
Also, depending on the perimeter he is usually travelling, it might be a good idea to check offers from local fare networks available in your home town (e.g. ZVV, Libero, Passepartout, etc.). They often have youth offers as well.
However, before his 16th birthday, he travels inexpensively using the Children day pass, whenever a single or return journey ticket (½ fare) is more expensive than CHF 19: https://www.sbb.ch/en/travelcards-and-tickets/tickets-for-switzerland/day-pass/day-pass-children.html
Get back to us should you have more questions.
Best,
Roland