Learning to write well begins at the sentence level.  Our youngest students can learn to write strong sentences with explicit instruction. An example from kindergarten: The live oak tree needs a lot of water.    We could expand this sentence into a compound sentence: The live oak tree needs a lot of water, but it doesn’t need a lot of sun.  Students learn that writing the word 'but' between two sentences means that the two ideas are in opposition to each other.  When we teach compound and complex sentences, we’re helping students understand the content and the structure of non-fiction writing. 

Link to The Writing Revolution webpage-Lots of free resources!

https://www.thewritingrevolution.org/resources/book-resources/

Online phonics diagnostic @whamphonics.com
Additional elementary resources @ https://www.teacherspayteachers.com/Store/Whamphonics