。
Every year I buy a new notebook for school use.
Literal
Every-year I [topic-は] school-use [as-として] new notebook [object-を] buy.
~として ('as X, in the capacity of X') is a set particle combination marking the function or role of the preceding noun. 学校用 uses the suffix ~用 ('for use as X') — productive for specifying function or target: 子供用 (for children), 業務用 (for business use).