Copyright guidelines for private online EFL teachers

I teach English online, but since I don't work for a public school or nonprofit, I'm unsure as to how to apply the fair use guidelines to my situation in order to avoid copyright infringement. If I use free articles/reading passages that I find on a website available to the public at no cost, can I use them in my lessons? Since they are free and accessible for my students either way, it seems like citing the source would make it fair, as the resources are already free, but I'm not 100% sure :/ (I live the the United States)