This paper reports on an in-depth interview study of the roles, job jurisdictions and associated learning of higher level teaching assistants (HLTAs). This role has the core purpose of covering classes to enable teacher release for planning, preparation and assessment. HLTAs' individual job jurisdictions are described and discussed as are implications for their knowledge and practice. The HLTAs are found to have wide-ranging job domains and, sometimes, unexpected involvements which mean they have to improvise practice. The study acknowledges that these HLTAs are being creatively managed and deployed by head teachers for the sake of teachers and schools. However, they are, at times, required to take on planning and cover duties which are beyond their knowledge and training with a likely impact on children's learning. Given their training and experience it is asked if covering classes to release teachers is the most effective use of their abilities and time. (Contains 1 table.)