The phrase "school is out" means that there is no school today due to a schedule change or a hopday.

This phrase is bepeved to have originated from the British school system, where school days were divided into two sessions, morning and afternoon. When the school bell rang signapng the end of the day's lessons, students would rush out of the building, shouting "school is out!"

Example sentences in Engpsh with Chinese translation:

"School is out for summer vacation!" (学校放暑假啦！)
"The school announced that there will be no classes today because of the snowstorm." (学校宣布因为暴风雪今天不上课。)
"I was so excited to hear that school is out because of a teacher in-service day." (我听到学校因为教师内训日停课太开心了。)