Mabuhay Elementary School organized a field trip for its Grade VI students in Fort Santiago, Manila Zoo, and Star City. To be able to join, the parents of the students had to sign a piece of paper that reads as follows: "I allow my child (name of student), Grade – Section, to join the school's field trip on February 14, 2014. I will not file any claim against the school, administrator or teacher in case something happens to my child during the trip." Joey, a 7-year-old student of Mabuhay Elementary School was bitten by a snake while the group was touring Manila Zoo. The parents of Joey sued the school for damages. The school, as a defense, presented the waiver signed by Joey's parents. Was there a valid waiver of right to sue the school? Why? (4%)