A drill school trains soldiers to obey standardised military procedures. It also allows military units to be recruited.
Drill is not simply a means of keeping soldiers busy by having the march up and down. On the battlefield all manouevres must be performed exactly, at the correct time, if a unit is not to be shot down or cut to pieces. Every man must be drilled to perform his part correctly when a unit moves from a line formation to a square, else confusion will result. Obedience to orders must be second nature: a soldier who is concentrating on not attracting the attention of his sergeant will also be too busy to worry about the enemy! Long hours of drill do have another, inadvertent benefit: men on a parade ground are not in the local tavern.
Drill, for all its boredom for the men, was a vital practice for all armies of the Napoleonic period. Even the armies of France realised that revolutionary zeal was not enough, and some order had to be brought to battle. Many armies, however, were late in adopting a single drill manual for their forces; for a few fortunate and literate officers, this was a godsend. They could earn quite handsome additional funds by producing privately written drill books.
Drill Schools are an upgrade from Barracks, requiring 3,000 gold and 7 turns. For all playable factions aside from Great Britain, Drill Schools are the lowest tier of military building that can train grenadiers and skirmishers. Drill Schools may be upgraded to Military Academies.