Antonios Giantzoglou, a student of Athens College Junior High School Grade 2, participated in the following tournaments as part of the Greek Children's National Team:

• In the Balkan Showjumping Championship, held in Kovilovo, Belgrade, from September 4 to 7, 2025. He achieved 4th place in the Children's Team category, and also secured 3rd place in the Children's 120 cm event.

• In the Children's Showjumping Cup, held from November 28-30, 2025, at the Markopoulo Olympic Equestrian Center in Attica. He achieved 1st place in the Children's category.

• In the Panhellenic Showjumping Races, held from December 3-7, 2025, at the Markopoulo Olympic Equestrian Center in Attica. He achieved 2nd place in the Children's category.

• In the Panhellenic Children's Showjumping Championship, held from June 25 to 28, 2026, at the Equestrian Center of Macedonia in Thessaloniki. He placed 2nd in the Children's category. He was also selected to join the Greek National Children's Team at the Balkan Showjumping Championship, to be held from September 10 to 13, 2026, at the Equestrian Center of Macedonia.