The Ebsib Is A Survey Aimed At Children Attending The 3Rd To 6Th Year Of Primary Education In The City Of Barcelona In The 2026/2027 Academic Year (Sample Frame Of 48,441 Children Enrolled In 322 Educational Centers In The 2025/2026 Academic Year). The Main Objective Is To Know The Level Of Well-Being Of The Child. The Main Field Work Sample Will Be About 5,000 Children. Considering That The Average Number Of Children In A Class Group Is 25, It Is Estimated That It Will Be Necessary To Survey Children From 57 Different Educational Centers, In Which 1 Or 2 Class Groups Will Have To Be Surveyed Per Year: 4,000 From 5Th And 6Th And 1,000 From 3Rd And 4Th (44 From The Same Schools).