Children are born naturally curious and eager to learn, but as they go through school this inner motivation to learn diminishes. Yet children’s inner motivation to learn is essential to deep learning, positive attitudes to school and wellbeing. Self-Determination Theory suggests that supporting children’s need for autonomy – that is to say the feeling that actions stem from internal sources rather than being imposed externally – is essential to supporting inner motivational resources. This thesis is concerned with how teachers may be able to support children’s autonomy and inner motivation in the early Primary classroom in England and how we may be able to capture changes in children’s inner motivation in those settings. It is divided into two parts. In Part I, I used interpretive methods to understand teachers’ attempts to provide greater opportunities for children’s autonomy in Year 1 classrooms through a professional development programme. This programme was developed by a team of researchers at the PEDAL centre using a Community of Practice model and involved nine teachers in trying out strategies to support children’s autonomy. Through stories of change, I show that teachers’ use and interpretations of the strategies varied, and this was affected by the teachers’ school context and their own beliefs. Through thematic analysis, I show that the classrooms in the study functioned as ecosystems of teacher control, which was itself under pressure from top-down directions through governmental policies and institutions as well as senior leaders. This resulted in a teaching mindset focused on strict learning objectives which left little space for children to take ownership of their learning. Despite this, teachers were sometimes able to provide pockets of space for children’s autonomy, though these took diverse forms. The extent of these spaces for autonomy depended on individual school and classroom contexts. The proposed model – pockets of space within an ecosystem of teacher control – explains the tensions between teachers’ need for control in the classroom and opportunities for children’s autonomy, as well as areas where teachers’ attempts to increase children’s autonomy were successful. In particular, I show that teachers needed to provide support and stimulation as well as space in order to support both autonomy and inner motivation. Part II is concerned with measuring inner motivation for research purposes and in particular for future evaluations of the above professional development programme. This research focuses on the validity and reliability of an existing instrument, the Leuven Involvement Scale (LIS). This instrument aims to capture a form of engagement in learning activities that is related to inner motivation. The studies in Part II investigate the reliability and stability of the instrument, as well as factors associated with variation in engagement using multilevel modelling. I found that the LIS can be reliable as long as raters share a common understanding of different child behaviours in the classroom. In addition, I found that engagement varied hugely from one moment to the next, with very little variation between children. What little variation existed between children was explained by the association between engagement and aspects of children’s self-regulatory capacities, namely effortful control and negative emotions, measured through the Strengths and Difficulties Questionnaire (SDQ) and Child Behaviour Questionnaire (CBQ). However, overall this research suggests that it is the individual moment that matters, rather than characteristics of the children. To better understand the influence of contextual factors, I investigated the association of activity setting (whether children are in teacher-directed, independent or free choice situations) with engagement. Children were significantly more engaged in free choice settings compared to whole class teacher-directed settings. However, there was a large amount of remaining variation and I discuss the implications this has for the role of teachers in supporting children’s engagement. Overall, this thesis makes a contribution towards our understanding of children’s autonomy and inner motivation in the classroom and teaching practices that support it, as well as how we may be able to study it in classroom contexts.