If students are doing research, your best bet is to check with your librarian. Many online databases have built-in dictionaries and read aloud tools for any browser. (In CCSD, our elementary students will see a read aloud option in Encyclopedia Britannica for any article, like pictured on the side. Secondary students will see similar options in the EBSCO database.)
If, however, you are using another website that doesn't have read aloud tools, you can try the Read & Write Extension for GoogleDocs. While this adds read aloud options to GoogleDocs, the extension will also appear in your Chrome URL bar so that you can highlight & read text (and this extension will highlight each word as it reads).
The Read & Write Extension for GoogleDocs has both a free version and a paid version. The free version includes the read aloud tool, but most of the other features are part of their paid product ($10 per user per year for groups of 150 or more).