A Westbury High School teacher was welcomed back to school on Monday after his battle with cancer.

Students and staff performed a flash mob to welcome social studies teacher Thomas Renner after his year-long battle with leukemia.

"I didn't know anything about it,” he said. “I just came in this morning my computer wasn't working I was just freaking out trying to get ready for my first period of class and they did this and really blew me away. It’s a good way to start the day and the rest of the year back."

Renner has taught at the high school for almost 20 years.