This article examines the extent to which occupations within a sector differ in their experiences of employer-led flexibility and in their responses through collective power. Three occupations are analysed in the Irish education sector - academics, school teachers and school secretaries. It might be expected that higher-level occupations would have greater sources of occupational power to resist employer-led flexibility. We find varying levels of employer-led flexibility through non-standard employment across and within occupations. We conclude that trade unions have achieved varying levels of success in negotiating regulations on casualisation, but that the effectiveness of union responses is likely to be dependent on the particular conditions which gave rise to casualisation amongst occupations. In terms of the propensity for each occupation to have standard or non-standard employment over a lifetime of employment, we conclude that school teachers can be categorised as an 'insider' occupation, that school secretaries have evolved to an 'outsider' occupation, while lecturing academics are most at risk of transitioning from an insider to an outsider occupation.