The first sentence has correct pronoun and antecedent agreement:
"When the teachers arrived at school, she saw the students writing with chalk."
However, it should be noted that "she" does not agree with "teachers," which is plural. So the ideal version would use "they" instead of "she."
Let's look at the other sentences:
- The second sentence contains a typo ("ther" should be "their" and "binarwery" should likely be "bin").
- The third sentence fails on agreement since "brothers" is plural but "he" is singular.
- The fourth sentence has a typo ("if" should be "it," and "ram jedvet" doesn't make sense in this context).
So, while the first sentence is technically correct, it would be better if it used a plural pronoun.