Teaching practice is considered a professional development tool for boosting science, technology and mathematics graduate teachers' employability. This study examined Nigerian school administrators' perception of the skills central to the employability of preservice STM teachers in order to make them work-ready when they graduate and increase their marketability in the transition from learning to earning. The study adopted a blueprint of mixed-methods approach. This approach offered an in-depth, contextualised, and natural but more time-consuming insight of qualitative research coupled with the more efficient but less rich of compelling predictive power of quantitative research. Data were collected using the semi-structured interview (qualitative data) with a protocol that comprised four open-ended questions involving 20 school administrators majorly Principals and a survey comprising 39 five-point Likert scale statements (quantitative data) from 180 school administrators (Principal, Vice Principal, Head of STM and Senior STM teachers) in 20 randomly selected senior secondary schools in Lagos State, Nigeria who offered three months of teaching practice for 98 preservice STM teachers in one university in Nigeria. The results showed a satisfactory level of preservice STM teachers' performance during the teaching practice as most administrators were in support of recruiting the preservice STM teachers in future. Teaching skills were ranked most important next to personal attributes for enhancing employability and needing most improvement by preservice STM teachers. The school administrators perceived the duration of the teaching practice to be too short and suggested an extension to twelve months for preservice STM teachers to benefit maximally from the training. They equally suggested that the preservice STM teachers on graduation should be posted to schools during the period of their National Youths Service Corps to further enrich their professional teacher training.