How to store multi-valued Field count in another field in solr

In my Solr Schema I have a multivalued field <field name="Student_id" type="string" indexed="true" stored="true"multiValued="true"/> I Want count the multivalued field. So I Am using schema.xml ->

In solrConfig I add following code

<updateRequestProcessorChain name="multivaluecountnum" default="true">
        <processor class="solr.CloneFieldUpdateProcessorFactory">
       <str name="source">Student_id</str>
       <str name="dest">Student_id_count</str>
     </processor>
     <processor class="solr.CountFieldValuesUpdateProcessorFactory">
       <str name="fieldName">Student_id_count</str>
     </processor>
     <processor class="solr.DefaultValueUpdateProcessorFactory">
       <str name="fieldName">Student_id_count</str>
       <int name="value">0</int>
     </processor>
     <processor class="solr.LogUpdateProcessorFactory" />
      <processor class="solr.RunUpdateProcessorFactory" />
     </updateRequestProcessorChain>
     <schemaFactory class="ClassicIndexSchemaFactory"/>
    </config>

But It's Not working. How to resolve my issue ?