"in the same school" is a perfectly acceptable phrase to use in written English.
For example, you could say "He and his brother attended classes in the same school for all four years of high school."
I think we're in the same school year".
it's the same children in the same school.
Or maybe they vacation in the same place, or have children in the same school.
Pupils and teachers in the same school were randomly assigned to three class types.
I used to play in the same school football team as Gareth Bale.
One of the worst was my own room in the same school.
Why this vast gulf between the state of the two cohorts in the same school?
Between them, the two families have three children in the same school.
He or she can then move on to a fresh start, sometimes in the same school.
Persistence of learning was examined later in the same school year and again two years later.
The Regents exams are typically scored in the same school where they are given, often by a student's own teacher.
