This article advances emerging scholarship that emphasizes the benefits to new institutional theories of organizational functioning offered by empirical research rooted in the tradition of symbolic interactionism. I present evidence from in-depth interviews with teachers from three high schools to show how individuals’ perspectives about pursuing institutional goals are filtered through their accumulated experience working within those institutions. Findings show teachers develop what I call “arsenals of teaching practice” as they accumulate work experience, and this process creates a key source of difference by career stage among teachers that shapes their instructional decisions. I discuss implications for understanding the relationship between policy and practice, and extend existing theory of inhabited institutions by identifying a key way that people’s sense-making through experience drives institutional functioning.