Easy Grammar by Wanda Phillips.
Consists of workbooks focusing on grammar skills for grades 3-6. The series focuses on recognition of prepositions and includes grammar concepts such as capitaliztion, punctuation and sentence structure. Separate teacher and student editions available.

REVIEW
Easy Grammar is a popular series that many people I know have found success using. It is very straight forward, workbook style approach. It doesn't require much, if any, planning from the teacher, just correction and there is a teacher's manual to assist with that job. It focuses a great deal on recognizing prepositions and building on grammar skills from there. Most children I have spoken with enjoy this series and the predictable pattern of each lesson. It would be easy to incorporate this curriculum in either a workbook style or unit study approach. Some people use Easy Grammar as their grammar curriculum. Others use it to supplement. Either way seems to work. It is a very versatile curriculum.