The COVID-19 pandemic disrupted students' daily life, but grit could have sustained students' wellbeing by helping them work hard and stay goal-oriented over time despite adversity. Gritty students may also have interpreted COVID-19-related adversity as an opportunity to grow, thus displaying higher levels of post-traumatic growth. In this study, 445 students in grades 6-12 (160 males, Mage = 14.25, SDage = 2.11) completed measures of grit and life satisfaction at the beginning (Time 1) and at the end (Time 2) of the school year, together with a measure of posttraumatic growth. A longitudinal SEM model shows that perseverance positively relates to posttraumatic growth, indirectly favoring life satisfaction at Time 2. In conclusion, perseverance, rather than consistency, appeared to have sustained students' positive adjustment to the COVID-19 pandemic. Teaching students how to nurture this quality can have important beneficial effects for their wellbeing under adverse conditions.