Using mobile technology and experience sampling in junior high school, real-time motivation and engagement were explored at four-levels: between lessons (up to 2 lessons per day; Level 1), between days (5 days per week; L2), between weeks (4 weeks; L3), and between students (113 students; L4). Findings for a 'random effects' model revealed substantial variance between students (M = 67%), followed by variance between lessons (M = 29%), with little variance between days and between weeks (M = 2%). In a 'fixed and random effects' model, we explored the roles of prior general academic motivation and engagement as well as ability and socio-demographics. Findings revealed that prior general academic motivation and engagement played a significant role in students' real-time motivation and engagement in mathematics and English and reduced between-student variance by about half. Gender (females), ability (high), and socioeconomic status (high) were also associated with higher real-time motivation and engagement.