The Southern needed a fast passenger locomotive for routes of medium importance, which admittedly allowed relatively high axle loads, but had a smaller loading gauge or shorter turntables. Since no locomotives with a 4-6-0 wheel arrangement could be used here, a locomotive with a 4-4-0 wheel arrangement that was as powerful as possible had to be developed. A higher axle load was also accepted and the Hastings line was rebuilt accordingly. The developed locomotive was the last in Great Britain with this wheel arrangement.

They took the Lord Nelson class as a model and developed a scaled-down version of it. Since its Belpaire firebox did not allow a driver's cab that fit into the loading gauge, a different boiler had to be used. This was found in the King Arthur class with a round-topped firebox. The firebox was adopted unchanged and the boiler barrel was shortened. With three cylinders, a starting tractive effort was achieved that was on par with the King Arthur.

The total of 40 locomotives were named after public schools, which is where the name “Schools class” came from. They were considered a very successful design right from the start and were the most powerful 4-4-0 locomotives in Europe. Despite the more even power development of the three cylinders, they tended to slip when starting due to the high tractive effort. However, they also performed well with poor coal. A locomotive made the run from London-Waterloo to Southampton with a 510 ton train at an average of 51 mph. The highest recorded speed is 95 mph. 

Over time, the locomotives received several improvements. From the second production batch smoke deflectors were installed and retrofitted to the first batch. 20 units later received a Lemaître blastpipe. Since this did not prove its worth, no more were converted. Under British Railways, they were also used in the Western Region and Wales. They were soon replaced by diesel-electric railcars and retired between 1961 and 1962.