Simple schema definition need some help

Here is my XML doc:

< ?xml version="1.0" encoding="UTF-8" ?>
< !DOCTYPE courses SYSTEM "http://www.school.com" >


< courses>
< course>
< department>Information Technology</department>
< course_name> OperSysConceptsandAdmn </course_name>
< course_number>IT 3423 </course_number>
< instructor>Susan Vande Ven</instructor>
< course_type lab="true" lecture="true">
< lab>false</lab>
< lecture>true</lecture>
< /course_type>
< time>5:30pm</time>
< room>J-266</room>
< /course>

< course>
< department>Information Technology</department>
< course_name>Intro Web Development</course_name>
< course_number>IT 3203</course_number>
< instructor>Brown</instructor>
< course_type lab="true" lecture="true">
< lab>true</lab>
< lecture>true</lecture>
< /course_type>
< time>7:30pm</time>
< room>J-210</room>
< /course>

< course>
< department>Information Technology</department>
< course_name>Advanced Application Development</course_name>
< course_number>IT 3883</course_number>
< instructor>Susan Vande Ven </instructor>
< course_type lab="true" lecture="true">
< lab>true</lab>
< lecture>true</lecture>
< /course_type>
< time>4:30pm</time>
< room>J-260</room>
< /course>


< /courses>

Here is what I have so far not sure even where to go because this is my first time creating a schema:
< xsd:schema
xmlns:xsd="http://www.school.com"
targetNamespace="http://www.school.com"
elementFormDefault="qualified">
< xsd:element name = "department">
< xsd:complexType>
< xsd:sequence>
< xsd:element name="course_name"
type="xsd:string" />
< xsd:element name="course_number"
type="xsd:string"
minOccurs="1"
maxOccurs="unbounded" />
< xsd:element name="course_number">
< xsd:simpleType>
< xsd:restriction base="xsd:integer">
< xsd:minInclusive value="1877"/>
< xsd:maxInclusive value="2100"/>
< /xsd:restriction>
< /xsd:simpleType>
< /xsd:element>
< /xsd:sequence>
< /xsd:complexType>
< /xsd:element>
< /xsd:schema> 25


Not sure what <xsd:minInclusive value="1877"/> <xsd:maxInclusive value="2100"/> is or </xsd:schema> 25 this is a template that I am using.
Not sure if I am heading even in the right direction???