What are the right technologies for educational web applications?

Hi, I have two main goals with my studies

A. Find a Job
B. Create, design, and Build educational web apps. What did they use to build sites such as funbrain or time4learning?.
I want mines to be better and include engaging animations, video, infographics to help children like my son who has some learning differences. I am just starting but would like to know I am learning the stuff I will need for both objectives.

So far I have HTML, CSS and JavaSript. Eager to use them in real life!
What else will I need for my educational Web apps?

Thank you in advance for your help!