Here is a rubric for sentence writing in grade 3:

4 - Advanced: - The sentence is complete and makes sense. - It begins with a capital letter and ends with the correct punctuation. - It includes descriptive words and details to enhance meaning. - The sentence demonstrates correct grammar, including subject-verb agreement and proper use of tenses. - The sentence shows a variety of sentence structures and lengths. - Spelling and punctuation are accurate.

3 - Proficient: - The sentence is complete and makes sense. - It begins with a capital letter and ends with the correct punctuation. - It includes some descriptive words and details. - The sentence demonstrates mostly correct grammar, with occasional errors in subject-verb agreement or tense usage. - The sentence shows some variety in sentence structures and lengths. - Spelling and punctuation are mostly accurate, with occasional errors.

2 - Developing: - The sentence is somewhat complete and makes some sense. - It begins with a capital letter and ends with some punctuation. - It lacks descriptive words and details. - The sentence demonstrates some errors in grammar, including subject-verb agreement and tense usage. - The sentence shows limited variety in sentence structures and lengths. - Spelling and punctuation have some errors.

1 - Beginning: - The sentence is incomplete or does not make sense. - It does not begin with a capital letter or end with the correct punctuation. - It lacks descriptive words and details. - The sentence demonstrates frequent errors in grammar, including subject-verb agreement and tense usage. - The sentence shows little to no variety in sentence structures and lengths. - Spelling and punctuation have frequent errors.

Note: This rubric can be adjusted and customized based on specific learning objectives and expectations for sentence writing in grade 3.