I have recently started using Teaching Writing Strategies from Prim-Ed with my class and it complements my grammar scheme really well. Here is an overview of both a junior level book and a senior level book.
Teaching Writing Strategies has six books in the series and would be suitable for 1st class to 6th class.
You could also differentiate easily by using lower level workbooks with your class. 
The books focus on the areas of word choices and sentence structure and punctuation along with a comprehensive section on editing and proofreading.
While they do not focus on specific genres they do teach specific skills and vocabulary that can be used to develop the children’s writing across all genres.
The books also contain self assessment grids for the children to use along with writing checklists. I have added these writing checklists to the writing portfolios of the children in my class.
I really like the layout of these books, they include short concise texts and activities for the children to complete independently or as part of group work or station teaching. In the Senior books it outlines specific details about the elements of grammar and specific rules for punctuation.
Sample of text from Book 1
Sample of text from Book 6
I also like the assessment sections available in all books in the series. You can focus on specific topics over a couple of weeks and then assess the children’s progress. The book also includes templates for teachers to record class progress.
The earlier books in the series would be ideal to link with the new Language Curriculum to achieve the learner outcomes within the understanding element of the writing curriculum.
If you want further information on these books check them out on the new Prim Ed Site.
A.M.
Aistear Múinteoir 