The species was first examined and named Sillago bassensis by Georges Cuvier in 1829 from the holotype specimen collected in Western Port of Victoria, which lies on the Bass Strait. A number of re-examinations of the fish commonly called 'school whiting' during the 1980s confirmed the presence of two possible subspecies, which were termed by McKay Sillago bassensis bassensis and Sillago bassensis flindersi, the Western school whiting and Eastern school whiting respectively. McKay hypothesized the two species diverged during the last ice age which left a land bridge from mainland Australia to Tasmania open during the Pleistocene, effectively isolating two pockets of fish, allowing genetic divergence. These two subspecies are now treated as separate species, despite a relatively young divergence time.
The identification of a further species of school whiting from Western Australia, Sillago vittata, caused the common name 'western school whiting' to applied to this species, while S. bassensis is now referred to as the 'Southern school whiting', causing some confusion. The species is often termed the 'silver whiting' by recreational fishermen in reference to the bright silvery longitudinal strip on the fish, while the name 'trawl whiting' refers to the fact large quantities are taken in commercial trawls.
The fin anatomy is highly useful for identification purposes, with the species having 10 to 12 spines in the first dorsal fin, with one spine and 18 or 19 soft rays on the second dorsal fin. The anal fin has two spines with 18 to 20 soft rays posterior to the spines. Lateral line scales and cheek scales are also distinctive, with southern school whiting possessing 63 to 70 lateral line scales and cheek scales positioned in 3-4 rows, all of which are ctenoid. The amount of vertebrae are also diagnostic, having 33 to 35 in total. The swim bladder has a short, blunt anterior median projection with no posterior projection.
The southern school whiting has a body colour of creamy brown to rusty above, before an abrupt transition to a silvery white below, with a brilliant longitudinal silver band separating the colours. A narrow rusty brown horizontal band is positioned above the silver band, with irregular red-brown oblique blotches and broken stripes positioned on the back and upper sides, much like Sillago maculata. The dorsal fins have rows of rusty brown or red-orange spots, the anal fins are yellow to hyaline in colour, while all other fins are pale cream, white or hyaline in appearance. There is no black blotch at the base of the pectoral fin.
The species is predominantly found over sand substrate in variable wave and tidal activity zones, often in protected bays. They often frequent the quiet waters of sand flats, the surf zones of beaches, as well as inhabiting deeper offshore waters to at least 55 m and possibly much deeper where they are taken by commercial trawlers over sand. Juveniles are usually found in a few centimeters of water on calm sand flats, in association with accumulations of detached macrophytes in the surf, but do not enter estuarine waters like many of their closest relatives, although they often occupy the sandflats at the entrances of large estuaries.
S. bassensis is known to spawn at three periods during the year, with the period between December and March the most common spawning time, with some individuals also spawning between September and November and in March and April. The presence of oocytes that range widely in size and development, as well as post-ovulatory follicles, suggest that the species is a multiple spawner.
The larvae of the species have a functional mouth and gut by 2.3 mm in length, with pigmented eyes and a gas bladder. By this time, the yolk absorption is complete. The snout of recently hatched larvae is concave, but changes to straight or slightly concave during development, as the mouth retracts from below the center of the eye to the anterior margin of the eye in older fish. The fins develop in sequence from caudal to pectoral, anal, 1st dorsal, 2nd dorsal and finally the pelvic fin. Scales are first visible around the gut and mid lateral line by 16 mm. The larvae of S. bassensis are the least pigmented of the whiting inhabiting southern Australia, with the lower jaw containing the only pigment for a long period of time. Juveniles migrate inshore to their nursery areas in surf zones and tidal flats, where they remain until reaching around 50 mm in length.
As southern school whiting mature, they move from their shallow near shore habitats to deeper offshore waters 20 to 35 m deep and within 20 km of the shore where spawning occurs.
The species is often taken by recreational fishermen, who do not normally target the species, often taking it amongst other deeper water whiting species such as S. robusta and Sillaginodes punctatus. The juveniles are often taken from the shore along beaches of variable wave action while fishing for species such as S. schomburgkii. Southern school whiting are taken on a variety of baits, with their natural prey such as marine worms, molluscs, prawns and sardines often used. Due to their schooling nature, many fish can be caught in a single fishing period, although most authorities ask for excess fish to be returned to the water alive. In Western Australia, southern school whiting and yellowfin whiting have a combined bag limit of 40 per person with no size restrictions, with no regulations applying elsewhere.