Hi Laura! According to the
Frequently Asked Questions section on the Disney website, the Magic Kingdom is busiest on Mondays, Thursdays, and Saturdays. Weekends are often busier than weekdays, since many local residents visit the parks then. For these reasons, as a general rule, you may find that Tuesdays and Wednesdays are quieter days at the Magic Kingdom. However, several factors can affect attendance levels at the parks, including the Extra Magic Hours schedule and the time of year. If you're planning a trip and trying to decide which day will be the least crowded, consider consulting the Crowd Calendar at the unofficial website www.touringplans.com, which predicts attendance levels in the parks by taking into account various factors such as Extra Magic Hours, historical crowd levels, special events, and more.
Hope this helps! Come visit us again at the Moms Panel if you have more questions!