Meaning of Inclusion

Recently I have been wrestling with what the true definition of inclusion is in schools.  The teachers and parents at my school seem to be split on what the true meaning is of this concept.  Some believe that inclusion refers to allowing all students to attend the school, regardless of the severity of their disability.  Their belief is that inclusion means that all students are welcome, and that whatever supports need to be in place to help those students succeed should be in place.  The other half of people believe that inclusion simply refers to having an inclusive class model, where all students participate in classes with both neurotypical students and students with special needs.  While this model means that all classes would be truly inclusive in nature, it also eliminates those students whose IEPs require a fully special education setting wherein there are no neurotypical peers.  I was just wondering if anyone had any opinions on this topic, and whether anyone elses' schools have struggled with defining inclusion and how it applies to an educational setting.