A group of larks is called an exaltation, widely considered one of the most beautiful and poetic entries in the entire English collective-noun tradition. The word likely draws on the skylark’s famous song, a high, continuous, almost joyful trilling delivered while the bird hovers far overhead, seemingly rising in celebration.
The skylark’s song has inspired poets for centuries, most famously Percy Bysshe Shelley’s “To a Skylark,” and “exaltation” fits neatly into that same tradition of treating the bird’s flight and voice as something close to spiritual. Larks sing almost exclusively while airborne, climbing to remarkable heights while maintaining an unbroken, complex song, a genuine feat of avian endurance.
Bonus fact: a skylark can sing continuously for several minutes without pause while climbing, descending, and hovering, all while maintaining the same intricate song pattern.
Larks are also occasionally described using more general bird terms like a flight or a bevy.
Related: Collective Nouns for Birds · What Is a Group of Larks Called?