two factors i would say that would be effective in an inclusive ethos would be  first one of caring  staff.

caring teachers, lead to a  caring student body which leads to increased student learning and  increased student participation.

Another factor I would say is how action oriented  members of staff are

for example if a student has a disability what steps do the teachers take how soon does help arrive for that student?

A positive ethos and learning environment whereby all pupils, including those with special educational needs, feel welcome and experience a sense of community and belonging. must be the ultimate goal of administrators only then would they be on their way of creating an effective school.