Kentucky fifth-grader Grace Reyes thought the biggest thing that was going to happen to her Wednesday morning was the monumental milestone of moving from elementary school to middle school.

Instead, Grace, a newly-minted graduate of Heartland Elementary School in Elizabethtown, Ky., got to see her father, U.S. Army Maj. Julian Reyes, for the first time in nearly one year.

Reyes hid in the basement of the family's home Tuesday night and then hid in the school principal's office Wednesday morning in order to surprise his daughter with her fifth grade diploma.

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"She was beyond excited and very much surprised," Heartland Principal Emily Campbell told ABC News. "It was very emotional."

Reyes, who is stationed in Korea and has done tours of duty in Afghanistan, was scheduled to arrive home in time to attend his older daughter's high school graduation this weekend, according to Campbell.

After Grace told her mom that, "I wish my dad could be here to see me graduate,' the family went into overdrive to make it happen.

"It happened really fast," said Campbell. "The mother contacted us the end of last week or Monday and told us that the dad was coming in and could we help."

At Wednesday's end-of-the-year ceremony at Heartland Elementary, Reyes, who could not be reached today by ABC News, hid behind the gymnasium's bleachers while he watched his daughter accept awards for being on the Honor Roll and others accomplishments.

When it came time for Grace to receive her completion certificate, Campbell purposely left out her name until the very end and then said a special guest was there to present her certificate.

When Reyes walked into view, Grace leapt into his arms and was overcome with emotion.

"It's really hard," Grace told local ABC affiliate WHAS. "It's hard to be without him and go through school and I'm very thankful he's here."

Grace checked out of school after the ceremony in order to spend time with her dad and her mom and two sisters, all of whom were in on the surprise, according to Campbell.

Reyes will be home with his family until November when he reports for his third tour of duty in Afghanistan, according to WHAS.