List View always returns first position

I'm making an app to manage my tests at school and it's almost done. However, I have a problem: when I want the position (int position) of the ListView, it ALWAYS returns the first position, even if I select the second position, for example.

public class ProvasActivity extends ListActivity implements AdapterView.OnItemClickListener, DialogInterface.OnClickListener {
    private List<Map<String, Object>> provas;
    private AlertDialog dialogConfirmarExclusao;
    private int provaSelecionada;
    private Aplicativo dao;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.provas_activity);

        dao = new Aplicativo(this);

        android.app.ActionBar actionBar = getActionBar();
        actionBar.setTitle("Minhas provas");

        actionBar.setHomeButtonEnabled(true);
        actionBar.setDisplayHomeAsUpEnabled(true);

        String[] de = {"materia", "conteudo"};
        int[] para = {R.id.materia, R.id.conteudo};

        SimpleAdapter adapter = new SimpleAdapter(this, listarProvas(), R.layout.provas_list_activity, de, para);
        setListAdapter(adapter);
        getListView().setOnItemClickListener(this);

        registerForContextMenu(getListView());

        this.dialogConfirmarExclusao = criarDialogConfirmarExclusao();
    }

    private List<Map<String, Object>> listarProvas() {

        provas = new ArrayList<Map<String, Object>>();

        List<Prova> listaProvas = dao.listarProvas();

        for (Prova prova : listaProvas) {

            Map<String, Object> item = new HashMap<String, Object>();

            Long id = prova.getId();
            String materia = prova.getMateria();

            item.put("id", prova.getId());

            item.put("materia", materia);

            provas.add(item);
        }

        return provas;
    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        Map<String, Object> map = provas.get(position);

        String materia = (String) map.get("materia");
        String msg = "Prova de " + materia;

        Toast.makeText(this, msg, Toast.LENGTH_SHORT).show();

        provaSelecionada = position;

    }

    @Override
    public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.provas_context_menu, menu);
    }

    public boolean onContextItemSelected(MenuItem item) {

        Intent intent;
        String id = String.valueOf(provas.get(provaSelecionada).get("id"));

        switch (item.getItemId()) {

            case R.id.remover:
                dialogConfirmarExclusao.show();
                break;

            case R.id.editar:
                intent = new Intent(this, NovaProvaActivity.class);
                intent.putExtra(Constantes.PROVA_ID, id);
                startActivity(intent);
                return true;
        }

        return super.onContextItemSelected(item);
    }

    @Override
    public void onClick(DialogInterface dialog, int item) {
        Intent intent;
        String id = String.valueOf(provas.get(provaSelecionada).get("id"));

        switch (item) {
            case DialogInterface.BUTTON_POSITIVE:
                provas.remove(provaSelecionada);
                dao.removerProva(id);
                getListView().invalidateViews();
                break;

            case DialogInterface.BUTTON_NEGATIVE:
                dialogConfirmarExclusao.dismiss();
                break;
        }
    }

    private AlertDialog criarDialogConfirmarExclusao() {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);

        builder.setMessage(R.string.confirmar_exlusao_prova);

        builder.setPositiveButton(getString(R.string.sim), (android.content.DialogInterface.OnClickListener) this);
        builder.setNegativeButton(getString(R.string.nao), (android.content.DialogInterface.OnClickListener) this);

        return builder.create();
    }

    @Override
    protected void onDestroy() {
        dao.close();
        super.onDestroy();
    }
}

How to solve?