校旗 is read as こうき (kouki) and means school flag.
こうき
kouki
こうしゃ
school building
こうえつ
revision
school discipline
しらはた
white flag
こっき
national flag
はた
banner (administrative division of Inner Mongolia)
せいじょうき
Star-Spangled Banner (US anthem)
はんき
standard of revolt
あかはた
Red Flag (Communist Party newspaper)
flag at half-mast
にっしょうき
the Japanese (rising sun) flag
たいかいはた
tournament flag