Keep checkbox array checked after submit-not working

I have refereed and tried many solutions provided in this type of question threads before asking my question as none of them working properly for me. I have one mysql table of students which stores stud name, marks. I am retrieving that data from database using while loop.

$query="select * from student";
$rs=  mysql_query($query) or die(mysql_error());


<?php if(mysql_num_rows($rs)){ ?>
  <table border="5" cellspacing="5" width="50%" align="center">
      <tr>
          <th>No</th>
          <th>Name</th>
          <th>Marks</th>
          <th>Operation</th>
          <th>  <input type ="submit" name="delete" value="Delete"></th>
      </tr>
      <?php


 while($row=mysql_fetch_array($rs))
          {


?>
      <tr>
           <th><?php echo $row['rollno']; ?></th>
          <th><?php echo $row['name']; ?></th>
          <th><?php echo $row['marks']; ?></th>
                      <th><a href="AllOperation.php?&no=<?php echo $row['rollno']; ?>&name=<?php echo $row['name']; ?>&marks=<?php echo $row['marks']; ?>">View</a></th>
          <th><input type="checkbox" name="check[]" value="<?php echo $row['marks']; ?>" <?php if(isset($_POST['check']))  if (in_array($row['marks'], $_POST['check'])) echo "checked='checked'"; ?> /></th>
      </tr>
      <tr>
      <?php  } ?>
<input type ="submit" name="total" value="total">

And i am generating the total of marks of all the students

if(isset($_POST['total']))


{                        $t=0;
                     foreach($_REQUEST['check'] as $val)
                     {                             
                         $t=$t+$val;                             
                     }
               echo "    total : ".$t;


 }

Now problem is that when first time i run the program it displays 5 student's information and than i selected first two checkbox and press the "total" button to generate the total. So it displays the total properly and keep that two check boxes checked. But when i checked third checkbox and press the "total" button than it shows the total of that three selected check box's marks but it display 4th or last checkbox checked even if i did't checked it. So why that is happening. See in above image- First i have selected checkbox of students a and b. so after pressing total it gave me total 2 and keep both the check boxes checked. Than i checked check box of student c and press the button "total" than it shows the total 4 properly. But makes the checkbox of student name "e" checked even if i didn't selected.