This error indicates that your school is listed as having a governance of CTC or non-maintained and that the 30 hour code has been entered for a student.
If this is the wrong governance for the school this can be amended via Admin > Config > Core Set Up > School and edit.
Alternatively if this is correct the 30 hour code on the pupil profile should be removed as they are not required for the census. To do this please search the pupil name in the top right hand search bar, go to the extended tab of the profile and underneath the school information heading delete the 30 hour code and save at the bottom.
