Two homes in the same Upper North Shore street can sit in different school intake areas. The suburb name in the listing does not settle the question.
Check the specific address using the NSW Department of Education School Finder. Check the primary and secondary schools separately, and confirm the position with the school if enrolment is central to the purchase. Boundaries and enrolment settings can change.
A catchment may affect what a particular family will pay, but it is not a standard percentage added to every home. Compare similar properties on either side of the relevant boundary and account for the other differences in land, traffic, walkability and street position.
Pay for a verified benefit you expect to use, not a sentence in the advertisement.