Here - I don't want to repeat the same ID, first name and last name to all the subjects so I used expand buttons. - This approach significantly reduces number of rows that are visible when all the rows are in a collapsed state.
But here one drawback is that, if number of subjects are say 10, I am leaving lots of vacant space ( marked with red border ). So need better solution on this problem. Popup is one of the approach but I would prefer any better approach.