This would indicate that no contracts in scope of the Census have a role of Head Teacher or Executive Head Teacher. If at present the school does not have someone in this role it would be necessary to annotate this when uploading your Census.
Alternatively to check the contract of the Headteacher please go to Admin > Personnel > Staff - find the Head Teacher's name - underneath the photograph of the Head Teacher ensure it says the below:
If not, click onto the text to amend this so that this staff member is collected by the Workforce Census. If this is correct check the contract by clicking onto the black cog next to the contract and ensuring that the post and role both state Head or Executive Head Teacher.