The "J" Sound is typically mastered by age 4.  See the video and resources below for more information and tips on how to make it.

High Frequency "J" Books

The Giant Jellybean Jar-  Marcie Aboff

Jackaloupe-  Janet Stevens

Jaguar's Jamboree-  Helen Moore

Jump!-  Scott Fischer

Jump Frog, Jump!-  Robert Kalan