Grouping problem

<?xml version="1.0"?>
<Root>
<State>
	<!--first standard; first lesson-->
	<Standard>
		<SS id="1.4.1">1.4.1  standard text </SS>
		<Lesson>Prefixes and Suffixes</Lesson>
	</Standard>

	<!--same standard as first; new lesson-->
	<Standard>
		<SS id="1.4.1">1.4.1  standard text</SS>
		<Lesson>Root Words</Lesson>
	</Standard>

	<!--new standard; new lesson-->	
	<Standard>
		<SS id="1.4.2">1.4.2  standard text</SS>
		<Lesson>Context Clues</Lesson>
	</Standard>

	<!--two standards grouped with one lesson-->	
	<Standard>
		<SS id="1.4.5">1.4.5  standard text/SS>
	        <SS id="1.4.6">1.4.6  standard text</SS>
		<Lesson>Synonyms</Lesson>
	</Standard>	
	. . .
</State>
</Root>

	<Standard>
		<SS id="1.4.1">1.4.1  standard text </SS>
		<Lesson>Prefixes and Suffixes</Lesson>
		<Lesson>Root Words</Lesson>
	</Standard>

<xsl:stylesheet version="2.0"
     xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" indent="no"/>

<xsl:template match="State">
  <xsl:for-each-group select="Standard/SS" group-by="@id">
      <xsl:for-each select="current-group()"/>
      <xsl:copy-of select="."/><xsl:text>&#10;</xsl:text>
      </xsl:for-each-group>
      </xsl:template>
</xsl:stylesheet>