Difficulty - killing from the passage is synonymous to the difficulty which means the hindrance associated with getting something done. According to the excerpt From the passage : It's killing these kids, killing here refers to the hardship and torment being faced by the student.
Antonym refers to the opposite meaning of a given word, same means something with similar or related characteristics, the opposite could be different which means the characteristics are not the same, similar or equal.
Partially means there exist a certain percentage or level of relationship or correlation, opposite could be entirely which means there is no degree of relationship no matter how small.
