tbody

<tbody>
            <?php
                $i = 1;
                while ($siswa = $listSiswa->fetch_array()) {
            ?>
            <tr>
                <td><?=  $i++ ?></td>
                <td><?= $siswa['nis'] ?></td>
                <td><?= $siswa['nama_lengkap'] ?></td>
                <td><?= $siswa['jenis_kelamin'] ?></td>
                <td><?= $siswa['kelas'] ?></td>
                <td><?= $siswa['jurusan'] ?></td>
            </tr>
        <?php } ?>
        </tbody>