The primary objective of this study is to examine changes in basic education teaching work from the perspective of teachers involved in union leadership in Brazil and Portugal. The thesis posits that we are experiencing a new phase of capitalist organization of labor processes, where digital technologies play a significant role in working time with collective consequences for health. Theoretically, the study employs parameters to analyze the limits of work hours, focusing on resistance and political struggle against old forms of exploitation and new forms of domination. In terms of research procedures, a qualitative social research approach was used with teacher unions in both countries, employing different investigative strategies. In Brazil, two workshops were conducted in digital environments with ten unionists, while in Portugal, individual interviews were carried out with five unionists. The field materials were analyzed using thematic analysis, resulting in three main analytical categories: flexibility and alienation of collective working time; technological time, burnout, and the right to disconnect from work; and time of resistance. According to the research participants, both countries experience issues such as overtime work, work overload, and a high volume of tasks. Despite the international weakness of unions, they remain important collectives fighting against the degradation of teaching work and advocating for quality education.