Anna Kepnershould’ve been walking across the stage with her classmates this weekend … instead, her grieving father accepted her diploma through tears as the crowd rose to its feet.

Christopher Kepner attended Temple Christian School’s commencement ceremony in Titusville, Florida … six months after Anna was killed aboard a Carnival cruise ship.

Watch the video, obtained by “Good Morning America,” that shows him wiping away tears as he walked onstage to collect Anna’s diploma following a standing ovation from the packed auditorium.

The heartbreaking moment became a tribute to Anna throughout the night … with Christopher, his wife Shauntel and other relatives wearing blue butterflies — Anna’s favorite — while Shauntel also created a senior table covered in photos of Anna and her friends over the years.

“It was hard,” Christopher said. “Being in her place to do that was very hard.”

He continued … “Our time with Anna was short, but it left us with many memories that we will forever cherish. We waited for her name to be called. I walked up and grabbed the diploma.”

The emotional ceremony unfolded as the criminal case surrounding Anna’s death continues to move toward trial. Her 16-year-old stepbrother, identified in court papers only as T.H., is scheduled to stand trial in September on federal murder and sexual assault charges tied to her death aboard the cruise ship.

Christopher and Shauntel also told GMA they remain “frustrated and upset” over a judge’s decision to allow T.H. to stay on pretrial release with a family member instead of in custody while awaiting trial.