private void btnAluno_Click(object sender, EventArgs e)
        {
            foreach (Form fr in this.OwnedForms)
            {
                if (fr.GetType() == typeof(frmAluno))
                {
                    fr.Activate();
                    return;
                }
            }
            frmAluno frm = new frmAluno();

            frm.al = this.al;
            frm.Show(this);
        }
        private void frmNotasDiciplinas_FormClosing(object sender, FormClosingEventArgs e)
        {
            frmAluno fr = (frmAluno)this.Owner;

            fr.al[idx].nt = this.nt;
        }