But as he grew older and moved to the United States to pursue a Major League Baseball career, the educational lessons Castilla turned to the most often transcended any single subject.
"Whether it was in school or in baseball, one thing I always remembered learning is to never take anything for granted," said Castilla, a former All-Star third baseman who spent nine of his 16 big league seasons with the Colorado Rockies. "Work hard and fight for what you want out of life. Never be satisfied. That stuck with me and is a strong message that I'll always carry with me."
It was a message Castilla shared with students at Barnum Elementary School in Denver on Thursday during a ribbon-cutting ceremony for the school's redesigned, cutting-edge library. The event was sponsored by Target, which, along with Major League Baseball and PEOPLE, is celebrating teachers who make an impact on the lives of their students and communities through the "Target Presents PEOPLE All-Star Teachers" campaign.
Through Tuesday, fans can nominate an outstanding teacher to give nominees a chance to represent their favorite team. The winning teachers will be honored at the 2014 MLB All-Star Game on July 15 in Minneapolis on FOX.
Castilla said he "didn't know any English at all" when he began his Major League career in 1991 with the Atlanta Braves, and learning a new language and adapting to a new culture certainly presented its own set of challenges. Soon, though, he became one of the Rockies' most popular players as a member of the Blake Street Bombers, and he has continued to use his stature to promote education in the Denver community since his retirement in 2006.
Myrella Goff, the principal at Barnum -- a school with a majority of students who speak both Spanish and English -- said Castilla's story resonated with her kids.
"You could see that they were thrilled," said Goff, who called the new library -- which included new computers, iPads, an interactive whiteboard and 2,000 new books -- the "highlight" of her career.
"And, too, they can identify with him. He came in speaking Spanish only. A lot of my students came into school that way, and they see, with him, the possibility of setting future goals and making them a reality."
Thursday's ribbon-cutting ceremony was also special for Susana Cordova, the chief academic officer for Denver Public Schools, who attended Barnum in the 1970s.
"I loved reading, and we didn't have a library half as big or half as beautiful," she said. "It's just so touching to see the lives of these children impacted and to see the collaboration of everyone in this community to give these kids what they need to do well in school."
Cordova believes Castilla's visit will have a lasting impact on Barnum's students.
"For them to see how successful he is," she said, "to see how staying in school and getting an education is important to him -- I think it's incredibly inspirational."