which one is correct? what is the difference? he is a teacher at many different high school not just one, so high school needs to be pluralized?
My father is a substitue teacher who teaches at high school
My father is a substitue teacher who teaches at high schools
at high schools: place
Meaning, he teaches at more than one high school
at high school: place
The meaning is awkward. Try,
Ex: My father is a substitute teacher who teaches high school.
Meaning, he teaches high school subjects at either one or more than one high school.
All the best.
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