aboth....and

[Lilish]

Hello there,

Would you kindly tell me which sentence is correct?

"Helen works both in a factory and in a highschool"
"Helen works both in a factory and highschool"
"in a" "is the similar structure in both sntences shall I repeat it after "and" like what I did in the first sentence?

Thank you all!

[Dozy]

These are the best coordinated:

"Helen works both in a factory and in a high school."
"Helen works in both a factory and a high school."

[AnWulf]

Ditto to what Dozy wrote: Helen works in both a factory and a high school.