In my school there is six grades. I am in  fifth grade. I learn math, PE, music, art, and English. There is a big  schoolyard. My favorite class is PE class. I love my school.

  Student's sentence            Corrected sentence            Grammar explanation          Better sentence     

Student’s Sentence: In my school there is six grades.
Corrected Sentence: In my school, there are six grades.
Grammar Explanation: We use “there are” for plural nouns like “grades,” not “there is.” A comma after an introductory phrase also improves clarity.
Better Sentence: In my school, there are six grades.

Student’s Sentence: My favorite class is PE class.
Corrected Sentence: My favorite class is PE.
Grammar Explanation: We avoid repetition when the subject is already clear. “PE” already refers to the class, so repeating “class” is unnecessary.
Better Sentence: My favorite class is PE.

Better Paragraph:
In my school, there are six grades. I am in fifth grade. I learn math, PE, music, art, and English. There is a big schoolyard. My favorite class is PE. I love my school.