The issue of authorship has been a thorny issue in academia. I'd like to ask for your insight into the authorship in the following situation:

My advisee's thesis is mainly and originally based on an innovative idea from me. After he graduated, I substantially revised more than 80% of his work, using a different analysis method to recode the data and revamping the introduction, literature review, discussion and conclusion sections. In other words, the revised paper, albeit being based on the student's raw data set, is already substantially different from the student's original work. 

The revised work was then submitted to a respected journal. I took care of all of the responses and revisions (3 rounds of major revision + 2 rounds of minor revision), and the paper finally got accepted. 

I listed my student as the coauthor (1st author) and myself as the corresponding author. But given my student's contribution to this publication, is he qualified as the first author? Or should he be listed as the secondary author? What should I do so that I can strike a balance between the ethical code and the effort I have put to this paper. Please advise. Thanks very much.