Disney normally classifies the 2 weeks prior and the 2 weeks after Easter as peak Spring Break season with extended hours, extra shows, etc. Since Easter falls at the end of March in 2008, I was counting on the end of March being peak season.
And yes, even though most CA schools may not have their Spring Break until Easter, many other schools have it earlier. Most of the school districts here in AZ will have their Spring Break in mid-March.