General Brazilian
campeonato de futebol júnior
Most common usage in Brazil
São Paulo
campeonato de futebol sub-18 / campeonato juvenil
Often uses age categories like sub-18, sub-15
Rio de Janeiro
campeonato carioca júnior
Regional variation including the state name
Portugal
campeonato de futebol juvenil / campeonato nacional júnior
Portuguese often use 'juvenil' instead of 'júnior'