Sentence frames provide students with the essential sentence parts provided. Students fill in the missing words and use these as foundation for discussions, sharing what they've learned, providing information, practicing description, compare and contrast, sequencing, etc. These are basic, but frames can be used to teach paragraph development too.
This ASCD site includes their growing resources around how to teach language and content at the same time. Watch video clips, find excellent texts, and hear how it's done.
"Contextualize the learning of language and literacy". Yep, that is what we're doing with SIOP. We are helping teachers become aware of the language skills (we generally take for granted) students need in their classrooms.