Writing prompt: The weekend is coming. Classmates, what are you planning to do? Using the given vocabulary and sentence patterns, and referring to the picture, write a short essay of about 60 words about your plans for the weekend.
Writing hints: be going to; do cleaning; visit grandparents; have a good time

Student essay:
This weekend is coming. On saturday morning, I clean my room. On saturday afternoon, i playing basketball with my friend. On sunday, i visit my grandparents. I have a good time.

Corrected essay:
This weekend is coming. On Saturday morning, I am going to clean my room. On Saturday afternoon, I am going to play basketball with my friend. On Sunday, I am going to visit my grandparents. I am going to have a good time.

Error analysis:
error_sentence: On saturday morning, I clean my room.
correct_sentence: On Saturday morning, I am going to clean my room.
error: saturday
correction: Saturday
error_type: Case Error
error_severity: 1
error_description: Case Error: According to English grammar rules, the day name 〈saturday〉 is a proper noun and requires capitalization; therefore, 〈saturday〉 is changed to 『Saturday』 to comply with English writing conventions.
error_sentence: On saturday morning, I clean my room.
correct_sentence: On Saturday morning, I am going to clean my room.
correction: am going to
error_type: Auxiliary Error
error_severity: 2
error_description: Auxiliary Error: According to the prompt requirements, the 'be going to' structure should be used to express future plans; the sentence 〈I clean my room〉 does not correctly use an auxiliary verb to indicate the planned future action, so 『am going to』 is added after 〈I〉 to clearly express the planned action.
error_sentence: On saturday afternoon, i playing basketball with my friend.
correct_sentence: On Saturday afternoon, I am going to play basketball with my friend.
error: saturday
correction: Saturday
error_type: Case Error
error_severity: 1
error_description: Case Error: According to English grammar rules, the day name 〈saturday〉 is a proper noun and requires capitalization; therefore, 〈saturday〉 is changed to 『Saturday』 to comply with English writing conventions.
error_sentence: On saturday afternoon, i playing basketball with my friend.
correct_sentence: On Saturday afternoon, I am going to play basketball with my friend.
error: i playing
correction: I am going to play
error_type: Verb Tense Error
error_severity: 4
error_description: ① Case Error: According to English writing conventions, the first letter of a word at the beginning of a sentence needs to be capitalized; therefore, 〈i〉 needs to be changed to 『I』 to comply with conventions; ② Verb Tense Error: The original verb 〈playing〉 lacks an auxiliary verb and tense marker; therefore, 〈playing〉 is changed to 『am going to play』 to indicate a future plan.
error_sentence: On sunday, i visit my grandparents.
correct_sentence: On Sunday, I am going to visit my grandparents.
error: sunday, i
correction: Sunday, I am going to
error_type: Auxiliary Error
error_severity: 4
error_description: ① Case Error: According to English grammar rules, the day name 〈sunday〉 is a proper noun and requires capitalization; therefore, 〈sunday〉 is changed to 『Sunday』 to comply with English writing conventions; ② Case Error: According to English writing conventions, the first letter of a word at the beginning of a sentence needs to be capitalized; therefore, 〈i〉 needs to be changed to 『I』 to comply with conventions; ③ Auxiliary Error: According to the prompt requirements, the 'be going to' structure should be used; therefore, 『am going to』 is added after 『I』 to clearly express the planned action.
error_sentence: I have a good time.
correct_sentence: I am going to have a good time.
correction: am going to
error_type: Auxiliary Error
error_severity: 3
error_description: Auxiliary Error: According to the prompt requirements, the 'be going to' structure should be used; therefore, 『am going to』 is added after 〈I〉 to clearly express the planned future action.