First go to System Preferences and select Dictation and Speech. Choose the Text to Speech button on the top and check Speak selected text when the key is pressed. When you highlight text and press Option and the esc key the text will be read on your Mac.
Now let's make the audible text usable for students who may need this accommodation. Highlight the text you want to record and right click on the area. Choose the last option on the drop down menu, Add to iTunes as a Spoken Track. Save the track to your desktop. You can add the track into Schoology (as a file or in a media album) and students can listen to the text. Please let me know if you need help. If you would like a link to the Google Slide Show of the steps please click here.