Another teacher here
!
Our Disney trips have occured in July, December (Xmas week--before New Years), and Spring Break in March.
Our most recent trip was this March (2009) during the week of St. Patrick's Day. It was by far the most crowded trip we've ever taken--except for maybe our Xmas trip! We took advantage of the 4/3 deal with the $200 gift card and apparently so did everyone else! We are quite experienced at dealing with crowds, getting up early, snagging FP at every opportunity, but we really felt the crowds on this trip! The weather was lovely and I don't even recall any rain!!!! We swam on several afternoons and the pool was pleasant.
We went in July 2008 and did not feel the same crowdedness. Of course, it was busy, but good planning is all it takes to have a wonderful trip. It was really hot, but we tried to make use of the pool as often as possible. Actually did the waterparks on this trip which my boys love (ages 12 and 8).
Our Xmas week trip was in 2006 and was still quite wonderful. We managed to get to parks for 7am openings and always did our favorite rides/attractions. It was crazy busy especially at AK. The beauty of the parks made it worth the hassle of getting up early. I loved the decorations. We had our ADR's and had wonderful meals. The weather was spotty. Some really rainy days wearing ponchos and blue jeans. Some cool days also. I don't believe we swam on this trip. Parks closed due to capacity, but we were usually ready to leave when it was peaking.
So, if I had to choose...the weather in March was the best. But due to a wonderful promotion, the hotels and parks were quite busy. The least crowds we dealt with were in late July, but it was hot hot hot! The Xmas trip was really special, had cool weather with occasional rain, and crazy crowds.
Whatever you do, I know you will enjoy yourself. Just make the best of it!
K