Hi Melissa!
Thank you for bringing your question to the Disney Parks Moms Panel!
I am like you, I prefer to travel when the crowds are lighter at
Walt Disney World Resort. As a general rule, when crowds are lighter, the prices are usually lower. The busiest seasons are considered "peak" and have the highest rates for rooms/tickets.
It makes sense that whenever schools are out, the crowds will be higher. Traveling in months that don't involve breaks (spring break, summer break, fall break) is your best bet. Long weekend holidays, like President's Day, are also busier than normal.
Early March would be OK, but spring break season begins in March and can be very crowded.
I like to use the website Touringplans.com to view a crowd prediction calendar. They use a ton of data to predict what the crowd levels will be like. It's just a prediction, but it is usually very accurate. It's a great tool for planning your trip.
I hope this helps! Please let me know if you have any other questions.