Cannot add or update a child row

import java.io.Serializable;
import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinColumns;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

import org.hibernate.annotations.ForeignKey;

@Entity
@Table(name="Avaliacao")
public class Avaliacao implements Serializable{
	
	private static final long serialVersionUID = 1L;
	@Id
	@GeneratedValue
	@Column(name="idAvaliacao", nullable=false)
	private int idAvaliacao;	
	
	@Column(name="dataAvaliacao", nullable=false)
	@Temporal(TemporalType.DATE)
	private Date dataAvaliacao;
	@Column(name="descricaoAvaliacao", nullable=false, length=45)
	private String descricaoAvaliacao;
	@Column(name="valorTotal", nullable=false)
	private float valorTotal;
	@Column(name="valorObtido", nullable=true)
	private float valorObtido;
	
	@ManyToOne(fetch = FetchType.LAZY)
	@JoinColumns({
		@JoinColumn(name="fk_fk_idPessoa", referencedColumnName="idPessoa", nullable=false)})
	@ForeignKey(name="FK_AvaliacaoAluno")
	private Aluno Aluno;
	@ManyToOne(fetch = FetchType.LAZY)
	@JoinColumns({
		@JoinColumn(name="fk_idTurma", referencedColumnName="idTurma", nullable=false)})
	@ForeignKey(name="FK_AvaliacaoTurma")
	private Turma Turma;

import java.io.Serializable;
import java.util.List;

import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.JoinColumn;
import javax.persistence.JoinColumns;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.PrimaryKeyJoinColumns;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table;

import org.hibernate.annotations.ForeignKey;

@Entity
@Table(name = "Aluno")
@PrimaryKeyJoinColumns(value={
	@PrimaryKeyJoinColumn(name ="idPessoaAluno", referencedColumnName ="idPessoa")})	
public class Aluno extends Pessoa implements Serializable{

	private static final long serialVersionUID = 1L;
	
	@ManyToOne(fetch = FetchType.LAZY)
	@JoinColumns({
		@JoinColumn(name="fk_idDesistencia", referencedColumnName="idDesistencia", nullable=true)})
	@ForeignKey(name="fk_idDesistencia")
	private Desistencia Desistencia;	
	
	@OneToMany(fetch = FetchType.LAZY, mappedBy = "Aluno")
	private List<AlunoTurma> AlunoTurma;
	@OneToMany(fetch = FetchType.LAZY, mappedBy = "Aluno")
	private List<Avaliacao> Avaliacao;