SALT LAKE CITY — With this year marking 20 years since “High School Musical” debuted on Disney Channel, the choice for the East High School theater class’s February production was an easy one. Luckily for the students, they got a truly rare opportunity when Lucas Grabeel — best known for his role as Ryan Evans in the “High School Musical” trilogy — dropped in on the group’s rehearsal Friday to offer his insight and expertise. I have never met and worked with a high school cast doing ‘High School Musical,'” Grabeel told the cast. Grabeel took time to talk to the cast, answering questions of all varieties and shining some light on the life of a working actor. Stay in school, care about your studies, try your best to pay attention and to care about everything,” Grabeel said.