Great Prep School is a private high school with a dress code that specifies the length of its students' hair. Harry who is a Great Prep student leases his hair grow long during his junior year as well as the summer preceding his senior year. At the foundation of Harry's senior year, school officials demand that he cut his hair or be expelled. Harry files a suit beside Great Prep. On what contractual grounds might Harry most effectively base his claim? Is the court probable to rule in Harry's favour on any of these grounds? Why or why not?