Off the top of my head for a quick run down
Could someone please post the high and low season + peak times for Disneyland?
Spring break in March, July + August, Mid December to about the 1st week of January.
Which months are low season?
When it rains earlier in the year January to April the crowds seem to be minimal. Granted its a trade off. Major rides and attractions go down for referb during these months. Usually right up until about May. September and November and early December are apparently really decent times to go as well as schools are back in.
When do the school holidays run?
Different districts are different. If your talking about for the Summer, the crowds start picking up after the first week of June. Spring Breaks usually the end of March.
Are there any other holidays I need to be aware of that could affect crowds at Disneyland?
Mothers Day, Easter, Memorial Day, Thanksgiving weekend, Watch out for grad nights during May and June, Halloween as they have Mickey's trick or treat which brings in people, Fathers Day, 4th of July