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Can I say,

One day morning, Chen Ling and his classmates had an English lesson at the classroom. After a few minutes, the fire alarm rang continuously. They were frightened.

Then, their class teacher instructed the pupils to line up. After lining up, the pupils walked to the school field. On the school field, there were many pupils.

After all pupils were on the school field, their classteacher arked the attendance of pupils. Then, the headmaster announced that there was a fire drill just now. The pupils listened carefully.
Comments  
In the morning,in the clasroom,marked the attendance of the pupils,then the headmaster announced that this was just a fire drill.

This sounds more proper.
Thanks, the others sentences are correct? which parts need to be corrected?