#objective based learning

Tomorrow I'm giving my 8th graders their first test.  I've made two versions.  One that's separated by the type of question (multiple choice, completion, etc).  And one that is separated by learning objective (for standards based grading).  I keep wavering.  I want to have a fully sbg 8th grade science class.   

Currently I have grades set up as 70% objectives, 25% tests, and 5% participation (to account for science notebooks and odds and ends).  I'm thinking of changing it to 80+% objectives (including tests) and -20% for their science notebooks to make sure they do their assignments (even though I won't be grading them).