Mom, what does you boy say when you sit down and calmly talk to him about why he is sad and crying? You need to really listen, it may help you find the answer. I teach young children and a little crying is not out of the ordinary for the first few wks, off and on as they adjust to the new, often more structured environment, and being away from Mom and Dad, but crying all day for a month is unusual. Ask yourself some questions Mom. Is your little boy overly sensitive? does he act this way if you leave him with a sitter? how is he at a relative's home without you? Is this unusual behavior for him; do you think it is separation anxiety? Are there siblings in the home who have just started school too ? Has anything changed within the last month that may bother him that he is not talking about? what's new at home? have u moved? marital problems? any job changes w/ Mom or Dad, losses of friends, family members or pets ? has he had any illness lately? Many simple changes in any of these area may cause him upset or sadness. How many days and hrs per wk does he go to in preschool? If he's there all day maybe it is too much for him at his age, can you change to a 1/2 day pgm? Ask yourself all of these questions to try to get to the bottom of things and make it better for him. If you can't figure it out soon, I would consider finding another place you can take him for childcare where he will be well cared for while you are at work. Maybe an in-home type child care arrangement would be better for him, at least until he is 4, then try again. Keep us posted, hope this helps.