In my kindergarten classroom, I use this rubric with our journals. Star writing has spaces between words, capital letters at the beginning of sentences, all of our rainbow (sight) words spelled correctly, an ending mark (punctuation), and 3 sentences about the topic.
Included in this file are color printable pieces for an anchor chart to remind them what 5 star writing looks like (I put mine in a star shaped pocket chart). It also includes a printable bookmark for their journals, and journal paper that you can "star" which of the 5 things the writer remembered in their writing.
I didn't even think about that..."rainbow words" is our sight word program. Send me an email at firstname.lastname@example.org and I will send you one that says sight words instead of rainbow words. Sorry about that. Thank you!