'But wait!', you say, noticing that balconies aren't technically a part of the ground-floor School Grounds area, 'This isn't right!' To which I say 'Fie on you and your silly logic!'
After the incident of 1986, the Balconies were deemed a part of the School Grounds for all intents and purposes. Primarily so they can act as a place where the rule against Public Displays of Affection at school can be circumvented. Because nothing says 'I wanna eat your face' like a balcony at sunset.