We want want to model teachers who have students and the parents of the students.

Naively, we start with a nice extension hierarchy: teacher.xsd

The key bit is this part:

<xs:element name="district" type="my:District"/>
<xs:complexType name="District">
   <xs:sequence>
      <xs:element ref="my:person" maxOccurs="unbounded"/>
   </xs:sequence>
</xs:complexType>

<xs:element name="person" type="my:PersonInfo"/>
<xs:complexType name="PersonInfo">
   <xs:sequence>
      <xs:element name="name" type="xs:string"/>
   </xs:sequence>
</xs:complexType>

Here we reference the "base type" of "PersonInfo" via an element in our content model for the type 'District'.

Regardless of type, the element name must be 'my:person' so the elements student/person/teacher can't be used.