"A bad school trip" 或 "a disastrous school trip" 可用来表示一次糟糕的学校旅行。
"Bad" 是形容词，意思是"坏的"， "disastrous" 是形容词，意思是"灾难性的" 。
举个例子：
The school trip was a bad experience for the students, as it was poorly organized and the weather was terrible.
The school trip was a disaster, with kids getting lost and no one knowing what to do.
上述例句的中文翻译分别是：
学校旅行对学生来说是一次糟糕的经历，因为组织得很差，天气也很糟糕。
学校旅行是一场灾难，孩子们迷路了，没人知道该怎么办。