Exploring Perimeter by Laura Candler - Comprehensive resource for developing and practicing perimeter concepts. Includes a wide variety of printables, lesson directions, and hands-on activitie, so it's a great tool for differentiating instruction. CCSS aligned with 3.MD.B.4, 3.MD.D.8, and 4.MD.A.3. $
Rainbow Editing - but I would use GREEN for capital letters on the first word in each sentence and proper nouns and RED for END punctuation. I teach sentence capitalization and end punctuation using the analogy of a stop light (green=go and red=stop), something they are all familiar with!