Colega poste seu codigo ai pra gente ver…
veja ai se seu turma.HBM se parece com isso, t+
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping
PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="beans.Turma">
<id name="id">
<generator class="increment"/>
</id>
<property name="nome"/>
<many-to-one
name="professor"
class="beans.Professor"
column="Professor_Pessoa_id"/>
<many-to-one
name="disciplina"
class="beans.Disciplina"
column="Disciplina_id"/>
<set name="alunos"
table="Turma_has_Aluno">
<key column="Turma_id"/>
<many-to-many
class="beans.Aluno"
column="Aluno_Pessoa_id"/>
</set>
</class>
<query name="buscarTurmasPeloNome">
<![CDATA[from Turma t where t.nome = :nome]]>
</query>
</hibernate-mapping>