Scratch Jr. is an iPad app designed for ages 5-7. Now that's a pretty narrow age range with very short attention spans.
While introducing a few programming concepts like sequencing and loops, the potential outcomes are limited. The programs a child can produce are more like short comic narratives than interactive games. Settings and characters are the most changeable, but cannot interact with each other through coding, nor do programs accept user input.
Designed to expose younger students to features in Scratch, the app may not have a wide appeal to first and second graders. I can see potential for the app in a classroom with teacher guidance and instruction, but it's not a typical entertainment app parents would give to a restless child. Once a child has mastered enough of the tools, and isn't bored, they will be ready to move up to Scratch where the possibilities are much greater.