Jellymetrics is a company that primarily offers email marketing services. They do offer one service that teachers could find handy. That service is the free Jellymetrics Readability Grader.

The Jellymetrics Readability Grader lets you quickly determine the readability of an article. To use the Jellymetrics Readability Grader simply copy text and paste it into the Readability Grader. The free tool then quickly analyzes the text and gives you a listing of the Flesch-Kincaid Reading Ease and grade level according to a handful of scales.

Applications for Education
The Jellymetrics Readability Grader could be a convenient tool to use when you’re selecting web articles to share with your students. The tool is good for typical web articles, but I think that it could be a bit cumbersome to try to copy and paste longer articles into the Jellymetrics Readability Grader.