Today's American educational context is characterised by increasing standardisation coupled with heightened accountability. While some view standardisation as a lever for equity, many view it as problematic for the work of teachers. Efforts to improve student achievement by focusing on the activities of teachers have resulted in an over-riding sense that teachers have lost control over their work and that teachers' professional identities are being worn away by the changes asked of them. Research has demonstrated the ways in which understandings of teachers' professionalism have changed over time. Here, I argue that not only have views of professionalism changed over time, but that different teachers or here different groups of teachers, experience and understand professionalism differently. In this article, I first look at teachers' professionalism across two decades using data from a large national database and then focus on how different generations of teachers experience professionalism in a context of standardisation in multiple ways based on qualitative interviews. The findings show that unlike veteran teachers from the Boomer generation (born 1943-1960) who started their careers as idealists but have become increasingly bitter about changes being asked of them, many Generation X (born 1961-1981) teachers are able to accommodate the changes asked of them in a more neutral fashion. While these teachers do not particularly like all aspects of standardisation, they feel that it is just part of the work they do, not who they are. This flexibility is not a function of diminished professionalism but rather a generational difference, as teachers from Generation X tend to be more flexible, less rule-bound than those from the Boomer generation whose mission is who they are. The data presented demonstrate the need to understand professionalism in a new light. Some teachers feel more control in this era of standardisation, and some feel less. Rather than viewing professionalism as a singular phenomenon that everyone experiences in the same way, it is increasingly important to view it as a complex phenomenon that can be experienced in unique ways at the same time by disparate groups of teachers. In this sense, professionalism can morph from more than "old" or "new" to complex, or what I term in this article "parallel professionalism."