Advances in technology have increased the opportunities for designers to personalise instruction based on student actions. We conducted semi-structured interviews with an international sample of educational professionals including researchers, teachers and designers, and reviewed interdisciplinary literature on personalisation to propose a framework for personalisation research and design. Thematic analysis of the interviews revealed that professionals value each type of personalisation opportunity (eg, customising for age-appropriate content, supports for student choice, automated guidance based on learner responses) and identify challenges (eg, trade-offs between adaptive and standardised instruction). Three research/design dilemmas emerged: individualisation and equity; group customisation and individual benefit; and adaptation and validity of measurement. We discuss these dilemmas in relation to three categories of personalisation: "customisation" by designers or teachers to support a specific audience (grade level, course, community); "individualisation" to support user choice (of book to read, project topic); and "adaptation" of instructional activities based on automated analysis of logged user performance (performance metrics, natural language processing, cumulative indicators). We suggest some guiding questions for a generative agenda for future research on personalised instruction.