老师帮忙看看，老是在xml最后一行报错

//plan.xsd
<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema">
    <element name="teachingPlan">
        <!-- comolexType标签含义是复杂节点，包含子节点时必须使用这个标签 -->
        <complexType>
            <sequence>
                <element name="course" minOccurs="1" maxOccurs="100">
                    <complexType>
                        <sequence>
                            <element name="course-name" type="string"></element>
                            <element name="class-hour" > 
                            <simpleType>
                            <restriction base="integer">
                            <minExclusive value="20"></minExclusive>
                            <maxExclusive value="110"></maxExclusive>
                            </restriction>
                            </simpleType>
                            </element>
                            <element name="exam-form" type="string"></element>
                        </sequence>
                        <attribute  name="id" type="string" use="required"></attribute>
                    </complexType>
                </element>
            </sequence>
        </complexType>
    </element>
</schema>

//plan.xml
<?xml version="1.0" encoding="UTF-8"?>
<teachingPlan
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:noNamespaceSchemalocation="plan.xsd">
    <!-- 教学计划 -->
    <teachingPlan>
        <!-- 大学英语 -->
        <course id="001">
            <course-name>大学英语</course-name>
            <class-hour>36</class-hour>
            <exam-form>考试</exam-form>
        </course>

        <!-- 高等数学 -->
        <course id="002">
            <course-name>高等数学</course-name>
            <class-hour>70</class-hour>
            <exam-form>考试</exam-form>
        </course>

        <!-- 计算机基础应用 -->
        <course id="003">
            <course-name>计算机基础应用</course-name>
            <class-hour>108</class-hour>
            <exam-form>上机考试</exam-form>
        </course>
    </teachingPlan>//这一行仍然报错