The teacher asked the students to "cease" talking or lose their privileges

The rain began early in the morning. It fell as hard drops, morning. It fell as hard drops, one after another. The sky one after another. The sky was full of dark purple clouds. was full of dark purple clouds. Thunder began as a soft Thunder began as a soft rumble and became louder rumble and became louder and louder. Lightning crashed and louder. Lightning crashed every few minutes, making the sky a brilliant white.

What is the main idea?