Well-being across the early years plays an important role for life-long quality or life and learning. We examine the measurement invariance of a school well-being measure (How I Feel About My School [HIFAMS]) across the UK and Hong Kong. In context of school closures during the COVID-19 pandemic, we also assessed the measurement invariance across cohorts tested online and in-person in both the UK and Hong Kong. We found configural, metric and partial-scalar invariance across countries and assessment modalities. Child HIFAMS scores were inversely related to parental SDQ ratings in the UK, but not in Hong Kong. COVID-19 restrictions were strongly associated with HIFAMS in both the UK and Hong Kong. Our results highlight the utility of HIFAMS across cultures and assessment modalities, however contextual factors of time (e.g., COVID-19 restrictions and resulting feelings about school and peers) and place need to be considered.