In this three minute clip, Stephen Krashen, celebrated scholar of linguistics, language acquisition and teaching, makes the case very clearly for comprehensible input.
The lesson still stands thirty years or so after this speech was made. Your students will stand a far better chance of acquiring English if you make the content of your lessons comprehensible.
The SIOP books in our professional library and resources online are the perfect starting point to understand how you do this. Drop by the EAL office if you want to explore some ideas.