After more than a year of searching, Boston school officials have found Madison Park Technical Vocational High School a new headmaster, who will take on the challenge of turning around the long-faltering school. Diane Ross Gary, who school officials say has extensive experience in vocational education, is expected to start her duties at the Roxbury school this month. Ross Gary is currently program manager for cooperative work education and college-career pathways at the Connecticut Department of Education. Previously, she served as an assistant principal and taught marketing and distributive education. “Dr. Ross Gary brings both extensive experience and a vision for the future of Madison Park, and we look forward to working with her on behalf of our students,” interim superintendent John McDonough wrote in a letter to Madison Park staff, students, and families Wednesday.