Higher Scores Test Prep
The way in which your SAT score is calculated depends upon the college you're applying to; however, averaging scores is not a common practice for undergraduate admission exams. Most colleges assess your SAT scores in one of two ways: generally, colleges either consider the highest score from a single test date or they "superscore" your SAT by taking your highest section scores (Reading, Math, and Writing) from various test dates and adding them together to create your best possible SAT score.
Which practice a school engages in is entirely dependent upon the admission office's preference and can change from year to year. Be sure to check with the colleges on your list to determine their preferred method of assessing the SAT.