Text-to-Speech
These two Google Extensions will read text out loud. Selection reader lets you select text to have read aloud. Announcify will blur out the text above and below letting the kids focus on what is being read.
Read&Write for Google Chrome
https://chrome.google.com/webstore/detail/readwrite-for-google-chro/inoeonmfapjbbkmdafoankkfajkcphgd
Read Aloud
https://chrome.google.com/webstore/detail/read-aloud-a-text-to-spee/hdhinadidafjejdhmfkjgnolgimiaplp
Voice Instead
https://chrome.google.com/webstore/detail/voice-instead/kphdioekpiaekpmlkhpaicehepbkccbf
You can see more details on each of these in a the following blog post
http://www.controlaltachieve.com/2016/10/special-needs-extensions.html