The purpose of this study was to explore the practices of multiage instruction with experts who have best practice knowledge or practitioner expertise in the multiage classroom. This investigation provided a foundation of knowledge on multiage instruction regarding strategies and challenges, the pros and cons of multiage instruction, and training and resources needed for the successful implementation of multiage instruction. A Delphi methodology was utilized which consisted of three rounds of surveys. The population comprised two panels of experts, multiage theory experts and multiage practitioner experts, based on required criteria for each panel set. A total of 21 experts completed Round One, which consisted of 55 Likert scale statements. A total of 20 experts completed Round Two, which consisted of 31 statements/questions. A total of 20 experts completed Round Three, which consisted of 29 statements. The panel experts in this study agreed that multiage instruction remains a credible practice today that should be recognized and supported by state boards of education. They also agreed that once oriented to the philosophy and after their child has spent time in the classroom, parents tend to be generally excited about the practice of multiage instruction. The experts further agreed that children of all abilities and needs can be successful in the multiage classroom. In terms of training and preparation, experts agreed that parents, teachers, school boards, principals, and superintendents all should receive training on the philosophy and strategies of multiage instruction in order for it to be a successful practice. They further agreed that it is difficult to find regular training and conferences geared for elementary teachers who work in multiage settings. In this study, panel experts identified strategies that multiage teachers use including how the room is arranged, flexible grouping, theme-based learning, collaborative learning, and peer mentoring. Through open-ended questioning, panelists also identified challenges as well as training and resource needs.