Does the goverment not trust the teachers' ability to just goddamn write down who's present?
Teaching system most likely designed to be faulty, government is mainly a mix of communists and profiteers, and Brazil is seemingly a laboratory for all that is bad and is to be applied in the world. 1984-style monitoring doesn't seem too far-fetched imo.
Bolsa Família is a government-run monetary aid, but irl it works as a dependency system, people on it never getting incentivized to leave. Feels like a way to pressure people on it into accepting the loss of privacy.
Also there appears to be a pretty big mass of the population that is utterly passive to abuses, so even without the pressure possibility, it's sadly unsurprising the state would feel bold enough to keep pushing.
By the way, students are forbidden to use cellphones in schools by law, the official reason being to focus on learning. But if memory serves me right, the law was passed around the time a lot of students were reporting with recordings teachers being ideological indoctrinators.