Sealed radioactive sources for school science became available during the 1950s from educational equipment suppliers and by the 1960s and early 1970s many UK secondary schools had purchased sets of them. These sources have been in use since then, which raises the question of their safe service life. A study was undertaken to examine the condition of a relatively large sample of school sources to see whether there are signs of source integrity beginning to fail and whether there are any patterns to failures, particularly those that may be age-related. The findings may be helpful to schools when undertaking reviews of the sources they hold and making judgements on keeping older sources in continued use.