Please see iSAMS Support ticket 688298.
We have a number of divisions within our iSAMS, two of which are junior schools. School one has year groups 1 to 6 which have the "NC Year" 1 to 6. School two has year groups 1 to 6 which have the "NC Year" 21 to 26.
Currently phase is set against the NC Year field in iSAMS, but this is a misnomer as it is the system ID for the year group, which means any year group outside of the range -1 to 13 is not included in the phase views in Central and thus the data is incomplete.
School Manager lets us set the DfE year group separately and this is limited to actual curriculum years which would make far more sense with the phase views in Central.