is Hebrew supported

Shalom Tal!

I assume you are referring to our TTS languages

No I'm sorry to day that Hebrew is not one of our built-in languages. 

But students (and teachers) can record their own voices in Hebrew (using the built in Microphone feature), or generate and upload audio that was generated on another website that supports Hebrew TTS 

For example: https://www.narakeet.com/app/text-to-audio/

All the best,

Gil

The Voki Team