Professor Johnson develops and teaches courses for Concord Law School at Purdue University Global, including Administrative Law, Constitutional Law, Education Law, and Special Education Law. He has written a number of books and articles on different areas of law including student speech and education issues. His books include Education Law: A Problem Based Approach, 4th Edition, Carolina Academic Press (2019), and Special Education Law, 5th Edition, Sage Publications (2020). He has also developed online interactive lessons on education law topics for the Center for Computer-Assisted Legal Instruction (CALI).
He also serves as a Hearing Officer for a state Department of Education, which includes the roles of mediator and administrative law judge. He previously practiced law and was counsel in a wide range of cases over the years including the Claremont v. Governor decisions in New Hampshire that established education as a fundamental right under the New Hampshire Constitution. He frequently appeared before administrative agencies, trial courts, the New Hampshire Supreme Court, and the First Circuit Court of Appeals. He has also participated in the legislative and political processes by working with legislators on drafting laws, testifying before legislative committees, and debating issues in various forums.