Clements is notable for reviving interest in the importance of perceptual and conceptual subitizing in early childhood mathematics education.
[5] Together with Julie Sarama, Clements developed the Building Blocks curriculum and the Learning Trajectories approach to early mathematics education.
[6] Clements has evaluated this approach in randomized controlled trials and shown it to have a positive impact on children's learning.
[7] This research has influenced evidence reviews and teaching guidance produced by the Education Endowment Foundation in the UK and the What Works Clearinghouse in the USA.
[8][9] Clements is married to fellow early mathematics researcher and collaborator Professor Julie Sarama.