A weighted rating such as Rw 45 dB is a single number derived from a measured curve. Two walls can both be rated 45 dB and behave differently: one may be weak at 500 Hz and strong at 100 Hz, the other the reverse. For a classroom, the weak point at speech frequencies is the one that matters.
The design target for a teaching space is usually expressed as a level difference between rooms, and it depends on the source level. A teacher speaking at normal effort produces around 60–65 dBA at 1 m; a class in group work produces more. If the adjacent room needs to stay below about 35–40 dBA to be usable, the required difference follows directly.
Practical school partitions therefore aim for a comfortable margin above the minimum: a 122 mm double-cavity wall with mineral wool and an acoustic board, sealed at every joint and penetration, with the door as part of the system rather than an afterthought. The door is usually the weakest element — a standard door set with an unsealed frame can lose 10 dB against the wall beside it.
The last point is the one that decides real performance: the wall is only as good as its flanking path. A wall that meets its rating but sits on a continuous screed, with a suspended ceiling above it and a service penetration at the skirting, will perform well below the laboratory figure. Detailing the flanking — the head, the base, the door and the services — is part of the specification, not a refinement of it.