上下课铃声怎么说英语

In English, the sound of a school bell ringing to indicate the start or end of a class is often referred to as the "school bell" or "bell for class." For example, you might say something like, "I heard the school bell ring, so I knew it was time to go to class," or "The bell for class just rang, so I have to go now." Other ways to refer to the sound of a school bell in English include "class bell," "school bell ringing," and "bell signaling the start or end of class."