php - drag sortable lists items to another div -

i'm building "project" school in php , i'm here because i'm having issues. i'll explain:

i have 4 lists of items , each 1 associated class (that user chose in configuration page) saved in database.
inside each list listed students belonging each class. using sortable jquery method able make can drag student class another, able , working intended.

i satisfied had far (since first time i've done similar). however, teacher asked me put below 4 lists rest of classes in divs or move student each of 4 "important" classes listed above 1 of "lets call other classes" making student change class (change field in table students via ajax or smthing) , make disappear page.

i dont know if made myself clear because english not i'll try make example.

let's had 7 classes in database. (a, b, c, d, e, f, g) , had defined "main" ones a, b, c , d. main classes in lists @ top , other 3 below lists (the difference wouldnt lists, wouldnt show associated students , if dragged student of main lists there). now there's important part
lets drag student list 1 (class a) div below corresponds class e, change students class e , remove page, or hide it, since doesnt belong of big classes anymore. this cant figure out how do

image understand: http://tinypic.com/view.php?pic=mtb96s&s=8#.vyp00plvhbc

image link2: http://prntscr.com/7irm41

does have suggestions of how achieve this? can post code let me know if need to

in query, can use order ordnung of elements.