Final answer:
The focus of a school nurse in the early 20th century was providing medical treatment to enable children to return to school.
Step-by-step explanation:
The focus of a school nurse in the early 20th century would have been providing medical treatment to enable children to return to school. During this time, public school enrollment was increasing and students were exposed to various illnesses. The school nurse played a crucial role in treating sick students and ensuring their well-being so that they could continue their education.