Transcript for Students give Philadelphia teacher the surprise of her life

relationship is often one of love or hate. But there's clearly nothing but love for one teacher in Philadelphia. Her students giving her the surprise of her life. Here's ABC's Ron Claiborne. Reporter: Quietly, the students at this catholic school were ushered in for the big surprise. A hero's welcome for teacher Mary polakow, returning for the first time since being treated for breast cancer. It's amazing. You pull for one another. It's just a shock to me. I didn't expect this. Reporter: Among those celebrating, Philadelphia Phillies player Brock Stassi. To see the difference we can make, it's incredible. It really -- really hits home. Reporter: The Phillies named pokalow one of their teacher all-stars. Recognizing her after a former student wrote to them about her teacher's courageous battle. I learned so much from her. Everything that she taught me I still use today. It was so inspiring to have her as my teacher. My students are everything and they're the reason -- I've been in education for 30 years. They're the reason I come back. Reporter: That same night polakow was honored again on the field before the Phillies game. Along with nine other teacher all-stars. A night of fun and an emotional outpouring for this beloved teacher who's in the fight of her life. And winning. Ron Claiborne, ABC news, new York. True school spirit. We thank Ron for that story. We thank you for watching. I'm Tom llamas in New York. Have a great evening. Good night.

This transcript has been automatically generated and may not be 100% accurate.