The Pirie-Kieren Model (PKM) was a paradigm shift in theories of learning by presenting a coherent, consistent theory compatible with complexity theory. PKM recognized that learning is non-linear, recursive, iterative, and emergent. PKM was one of the first theories to depart from the linear models of learning that dominated theories of learning prior to PKM. One of the critical concepts in PKM is folding back. This paper considers implications from PKM: Implications for practice and implications for theory. For practice, PKM has implications for both instruction and for assessment. Teachers need to be given theories of teaching that are congruent with PKM's non-linear and recursive model of learning. Teachers need such theories of teaching to recognize the elements of PKM such as non-linearity, recursiveness, iterations, and emergence. For assessment, since one of the implications of PKM is that each student will typically be at different points in their learning at any particular time, mass norm-referenced or criterion-based assessments are clearly inappropriate, and other assessment models, such as ipsative assessment, need to be implemented for appropriate assessment of learning.