I'm trying to figure out how to check if a node has children in xslt in 4.5 schema...

In this navigation xslt:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE xsl:stylesheet [ <!ENTITY nbsp "&#x00A0;"> ]>
<xsl:stylesheet
  version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:msxml="urn:schemas-microsoft-com:xslt"
  xmlns:umbraco.library="urn:umbraco.library" xmlns:Exslt.ExsltCommon="urn:Exslt.ExsltCommon" xmlns:Exslt.ExsltDatesAndTimes="urn:Exslt.ExsltDatesAndTimes" xmlns:Exslt.ExsltMath="urn:Exslt.ExsltMath" xmlns:Exslt.ExsltRegularExpressions="urn:Exslt.ExsltRegularExpressions" xmlns:Exslt.ExsltStrings="urn:Exslt.ExsltStrings" xmlns:Exslt.ExsltSets="urn:Exslt.ExsltSets"
  exclude-result-prefixes="msxml
 umbraco.library Exslt.ExsltCommon Exslt.ExsltDatesAndTimes 
Exslt.ExsltMath Exslt.ExsltRegularExpressions Exslt.ExsltStrings 
Exslt.ExsltSets ">

<xsl:output method="xml" omit-xml-declaration="yes" />

<xsl:param name="currentPage"/>

<!-- Input the documenttype you want here -->
<xsl:variable name="level" select="2"/>

<xsl:template match="/">
<!-- The fun starts here -->
  <xsl:for-each select="$currentPage/ancestor-or-self::* [@level=$level]/* [@isDoc and string(umbracoNaviHide) != '1']">
    <xsl:if test="$currentPage/@id = current()/@id or $currentPage/../@id = current()/@id or $currentPage/../../@id = current()/@id">
      <!-- output navigation Title -->
      <a class="leftnavtitle" href="{umbraco.library:NiceUrl(@id)}">
        <xsl:value-of select="@nodeName"/>
      </a>
      <ul>
        <!-- 1st navigation items -->
        <xsl:for-each select="./child::* [@isDoc]">
          <xsl:if test="$currentPage/ancestor-or-self::node/@id = current()/@id"></xsl:if>
          <li>
            <a href="{umbraco.library:NiceUrl(@id)}">
               <xsl:if test="@id = $currentPage/@id"><xsl:attribute name="class">selected</xsl:attribute></xsl:if>
              <xsl:value-of select="@nodeName"/>a: <xsl:value-of select="count(./descendant/* [@isDoc])"/>
            </a>
          
          <!--output 2nd level nevigation items -->
            <xsl:if test="$currentPage/@id = current()/@id or $currentPage/../@id = current()/@id or $currentPage/../../@id = current()/@id">
          
              <ul>
                <!--output 3rd level nevigation items -->
                <xsl:for-each select="./child::* [@isDoc]">
          
                <xsl:if test="$currentPage/ancestor-or-self::node/@id = current()/@id"></xsl:if>
                <li>
                  <a href="{umbraco.library:NiceUrl(@id)}">
                    <xsl:if test="@id = $currentPage/@id"><xsl:attribute name="class">selected</xsl:attribute></xsl:if>
                   <xsl:value-of select="@nodeName"/>b: <xsl:value-of select="count(./descendant/* [@isDoc])"/>
                  </a>
                </li>
                </xsl:for-each>
              </ul>
            </xsl:if>
            <!--end of 4th level children -->
            </li>
          </xsl:for-each>
        </ul>
      </xsl:if>
    </xsl:for-each>
</xsl:template>

</xsl:stylesheet>

This line always returns 0:

<xsl:value-of select="count(./descendant/* [@isDoc])"/>