Pivetada is a Brazilian Portuguese slang term, particularly common in the periphery (favelas and working-class neighborhoods), referring to a group of kids or youngsters.
It's a colloquial and somewhat informal term that perfectly captures the street-level perspective of the song. While a more common word for kids is "crianças," "pivetada" carries a specific cultural weight, evoking the youth growing up in the challenging environment described in the lyrics.
Racionais MC's takes us on a gritty tour of the periferia (periphery), a place that's a "pesadelo periférico" [peripheral nightmare]. It's a place where kids head to school by day, but by night, "os manos decola na farinha hã, na pedra hã" [the homies take off on flour, huh, on rock, huh], getting high. The artist feels for their families, and for the young ones who see these bad examples.
This song is a stark look at the struggles of the working class in these areas. The head of the house is always working, "escravo do dinheiro" [a slave to money], just to put food on the table. The system, the song says, manipulates people, making them forget how to stand on their own. It's a place where tears are too common, like a "filme de guerra" [war movie]. The vision here isn't beautiful, and there's no other place like it. The song hammers home the point: "Periferia é periferia" [Periphery is periphery].