Assessment is a good idea, but not grades. Let me explain the difference. Assessment is an evaluation of whether a child understands something/has mastered something. Grades are just a letter number assigned to that, which is helpful for teachers in comparing a child to the rest of the class or evaluating the status of a class as a whole, and are also used to let parents know how a child is doing. But at home you don’t need to have a letter grade (and really, converting your assessment to a letter grade can take a good bit of time, so I suggest not bothering with it). You just need to know whether your child is learning, and you can tell that without a grade.
Lets put this another way…those letters aren’t very helpful in showing your child where they need to improve because a letter grade is abstract. They’re not very helpful in showing you how to help your child for the same reason. It’s better to just tell your child what they need to work on: (IE, your handwriting is improving, but you still have trouble with spaces between your words, which make your writing hard to read. You are doing very well in addition…you have all your addition facts memorized, except you need a little work on adding 7s.)
Remember how in kindergarten, in stead of giving a letter grade, they gave a list of skills that the child was learning. (The list would include different skills like “is able to count to 10” and “can spell own name” and then would have a + for mastered and a - for “still developing” and might have even included a list of all the letter sounds he was learning, with check marks on the ones he learned.)
Something like that would probably be more helpful for you. You can make one up yourself using any site listing a “scope and sequence” for a grade level ( in homeschooling you don’t have to go by grade…but the lists can still be helpful in compiling your goals). Leap Frog has a good list: http://www.leapfrog.com/en-us/learning-path/articles/first-grade-skills-checklist (that page is for what they should have learned before entering first grade, so it’s what a child should learn in kindergarten…they have articles for every grade but I can’t seem to find where they list all of them on the site, so in that URL I just replace first-grade with second-grade or kindergarten and it takes me to the grade I want). You can look up the TAKS for your grade level, but honestly I find those kind of confusing.
Then you just check for mastery every now and then (this can be by having a child explain back a concept to you, having them do an assignment without help, which can work like a test even if you don’t call it test, or just carefully observing them and taking notes).
Whether you decide you want to use a letter grade or not, I find rubrics can be a good way of assessing things that are a little more complex (like how well a child is doing on writing essays or creative writing). I used these when I was middle school English teacher (briefly…and please don’t judge my teaching by my typos, cause I don’t stop to edit here). Here’s an example of one for an essay: http://www.slideshare.net/pjlynch/essay-assessment-rubric
Using rubrics make it easier to make a letter grade for writing assignments and projects if you want to do that, but also are more helpful to the student than just a letter because they help esplain why they got that grade. Here’s a place where you can find a lot of editable rubrics for various subjects: http://rubistar.4teachers.org/index.php?
Another thing that helps is keeping work, so that you can compare a child’s previous work to what they are doing now and note progress.
Hope this helps.
Good luck!!