Marc began teaching in 1988, teaching in three different schools in the south Wales valleys, before returning to the north in 2001 to lead Ysgol Gymraeg Croes Atti, Flint. He is now the head of Ysgol Pen Barras in Ruthin.

Marc has benefited greatly from being involved in and leading or chairing a number of local and national committees and working groups. He chairs his cluster, and represents the cluster on a number of committees, such as the Welsh Language Strategic Board, Finance Forum and Chairman of the Flintshire Federation of Heads. At a national level, he has been a member of the Schools Workload Reduction Panel (SWAP) and has been part of a headteachers working group with Estyn looking at the new inspection framework as well as being a peer inspector with Estyn, since 2011.