Background: Previous research has argued that classroom assistants (CA) need training which is purposely aimed at enriching their pedagogical role with regards to CA-pupil interactions (Blatchford et al., 2009a; Blatchford et al., 2009b; Webster et al. 2011; Webster et al., 2013). Aim: To evaluate how CAs mediate the learning material to the pupil they support before and after training in MLE. Sample: Two CA-pupil dyads were recruited from one post-primary grammar school in NI. Methods: A one group pre-test post-test mixed method design using observational measures (video recording) was used. CA-pupil dyads were video recorded before training and four weeks after training. Training consisted of one day on mediated learning experience (M LE). The quantitative analysis was informed by the principles of content analysis whilst qualitative analysis was informed by the principles of conversational analysis. Results: The frequency and quality of mediation behaviours, for both CAs, changed after training. Prior to training CAs' MLE behaviours hindered the pupil from learning. After training, both CAs demonstrated facilitation of the pupil's learning by eliciting meta-cognitions and by working within their zone of proximal development (ZPD). Conclusions: Training in MLE increased the CAs understanding of the needs of the pupils they support by working more within their ZPD, which improved the quality of the mediation to the pupils they supported.