SAT score fluctuation?

Hello parents,
I am currently studying for the SAT and my scores have been fluctuating frequently. For example, my writing score can go up to 710 the first week and lower to 610 the following week. Has your child experienced the same situation before? Though it is natural to fluctuate between a few points, I find it hard to believe that scores can drop or rise 100 points between just one test in a week!