The Royal Academy
The Royal Academy in France, founded in 1648 (there was also one in England) was an arm of the monarchy. The kinds of France, and the ruling parties, always recognized that controlling what art looked like and what it was about, was a way of controlling or changing the opinions of others. The is one on the primary reasons that art was always seen as so politically charged -- if you went against the rules of art, you were a rebel against the government. The Royal Academy essentially controlled teaching art (it ran the Ecole des Beaux Arts -- the School of Fine Arts), and the exhibiting of art (by running exhibitions every year or two called the "salon"). For much of its history, the Royal Academy (made up of members appointed for life - so you can imagine their average age) promoted art that was based on ancient Greek and Roman art, and the art of the Renaissance. These were upheld as the single definition of beauty that all artists must follow.
Hierarchy of Subjects
In addition, the Academy created a hierarchy of subjects, with history painting as the most elevated subject, and still-life and portraits as the lowest. History paintings (which included noble historic moments, ancient Greek and Roman mythology, and biblical subjects) were held to be the highest because they depicted heroic figures ans subjects in scenes where the composition was invented by the artist. Still-life painting and portraits were held to be the lowest because there was no invention in that case by the artist, who was, in this view, simply painting what was in front of them. Genre scenes, or paintings of every day life, were also a lowly subject because they did not offer the heroic and noble.
Prix de Rome
The Royal Academy sponsored a rigorous yearly competition, the Prix de Rome. The winning artist got time to study at the French Academy in Rome. In the last half of the nineteenth century, the art that was favored by the academy and by the public was a watered-down version of history painting -- quaint, sentimental images with a clear narrative and a studied realism.