At some airports if your flight is "clean" you will be directed at the jetway directly to the departures level (for transit passengers), otherwise transit passengers will be directed to the arrivals level for subsequent transfer processing. Usually arrivals and departures are on 2 different levels.

Singapore Changi is an example of an exception to this (I know it isn't Schengen). At Changi arriving and departing passengers mingle in the same spaces and this requires departing security at the gate.