codeSpark Academy is a wonderful free iOS app for students learning how to code/program ages 4-9 yrs old. Kids learn how to code by simple step-by-step instructions where they interact in the Foo Studio. This is done by dropping blocks of code and watching the actions they preform. Also, there are projects, activities, and printables, that help teach coding. This is an ideal way to introduce STEM into the curriculum.
I highly recommend checking out codeSpark Academy by clicking here!!!