The education of Hogwarts students is put in jeopardy in Harry Potter and the Order of the Phoenix (2007). For the first time in Harry’s (Daniel Radcliffe) life, he truly seems to appreciate the value of his education and fears for his classmates when the suitability of their coursework comes into question.
Following the dark events that unfold at the end of Harry Potter and the Goblet of Fire (2005), Hogwarts is gradually commandeered by The Ministry of Magic, the corrupt and broken organization that oversees the acceptable use of magic and enforces magical law within the wizarding world. A monstrous woman by the name of Dolores Umbridge (Imelda Staunton) is installed as the Defense Against the Dark Arts teacher and later gains promotion to High Inquisitor at Hogwarts, effectively usurping power from Dumbledore (Michael Gambon) and putting control of the institution’s students, teachers, and curriculum in the hands of the Ministry.
Umbridge is instructed to teach only theoretical defensive ideas and not anything her students can actually practice. This move is one of self-preservation by the Ministry, who believes the recently-returned Lord Voldemort (Ralph Fiennes) plans to use the Hogwarts student body to attack and destroy the Ministry. Umbridge, a ruthless and dictatorial overseer, also sanctions an “Inquisitorial Squad” built entirely of Slytherin students, which rewards individuals for spying on one another. She further imposes cruel and abusive punishments on students she dislikes or who break even the most trivial of her oppressive rules.
Umbridge and the Ministry’s manipulation of the Defense Against the Dark Arts curriculum comes at the most devastating time in Hogwarts students’ lives. With dark arts on the rise in the world and Voldemort returning to power, it is more important than ever that they learn to defend themselves against attack. This prompts Harry and others to form a secret study group called Dumbledore’s Army, or the D.A. for short, which operates in a magical room called the Room of Requirement (it becomes suitable space for whatever someone needs). Harry, proving to be an effective and powerful wizard through the events of the first four films, serves as the D.A.’s primary teacher. He instructs a group of students defensive spells, offensive attacks, and advanced techniques like the patronus -- a means of shielding oneself from the soul-sucking assault of a Dementor, the universe’s prison guards who are at the mercy of the Ministry.
Though the group is eventually discovered, the hard work and training they find within a voluntary community education setting ends up saving them at the end of the film when many students find themselves cornered by a fleet of Death Eaters. The group manages to escape mostly unharmed thanks to their collective training from the D.A. Had they not been so proactive in maintaining legitimacy to their education, this might not have been true.
Dumbledore’s Army stands as a confirmation of the value of the education the kids receive at Hogwarts, as well as a testament to the character of student it produces. When denied the necessary progression of their education, they are determined to get it through other means.
It also speaks to the importance of unity within the student body. Hogwarts is a naturally segregated school -- students are funneled into one of four houses who compete against one another through sports, academics, and somewhat arbitrarily-administered points for various accomplishments throughout the year. Each house represents one of Hogwarts’ founders and each has their own idealized views and perspectives on education and society. As the Ministry injects itself in the academic setting, this internal splintering of houses becomes even greater. Umbridge’s Inquisitorial Squad severely damages inter-house relations as students begin reporting to the authorities on each other’s behavior. Dumbledore's Army looks beyond houses, class, and age. It is not selective, but unified, accepting anyone who wants to get the real education they deserve and need to be safe and strong in an ever-darkening world.
While Hogwarts can, at times, appear a magical playground for kids to learn tricks, the value of the institution as a place of learning is most apparent in The Order of the Phoenix above all the other films.