显示包含选项中数据的所有记录

I want to echo all of the data that contains the selected option but every time I echo those data, I only get one.

the select is use for filtering the search, here's my code

<select class = "grade" name = "grade">
<option value ="" >=====Grade=====</option>
            <option value ="Grade11">Grade 11</option>
            <option value ="Grade12">Grade 12</option>
</select>
<input type="submit" name="search" value= "Submit">

</div>
<div class = "records">
    <table width ="600" border = "1" cellpadding ="1" cellspacing ="1">
        <tr>
            <th>Last Name</th>
            <th>First Name</th>
            <th>Middle Name</th>
</tr>
</table>
<?php
if (isset($_POST['search'])) {


    $grade =$_POST['grade'];
    $sql = "SELECT * FROM student WHERE grade ='$grade'";
    $result = mysqli_query($conn, $sql);
    $row = mysqli_fetch_assoc($result);

   echo "<tr>";
        echo "<td>".$row['lname']."</td>";
   echo "</tr>";

}

You missed while loop.. It will print all data from result..

while($row = mysqli_fetch_assoc($result))
{
   echo "<tr>";
        echo "<td>".$row['lname']."</td>";
   echo "</tr>";
}