My daughter started the "Montessori based" school at two and a half. And that was the first time that she had ever been in any sort of care other than family or friends (I did leave her with close friends and grandma pretty regularly). I too needed some time alone with the new baby. And she needed some time that wasn't dominated by new baby.

So...my best advice? Know what you're going to do when you drop her off. She may not be upset the first time or two, but there will very likely come a time when she clings to you and says "Mommy, don't leave me!". Or cries. Be ready. Have a plan. Will you hug her, say "mommy always comes back" and pass her over to a teacher and then walk away? Will you say "I'll stay for one story and then I have to go", and then leave when you say you will? Will you stay for the day to get her comfortable? Will you just say "I have to go now" and leave? There are a lot of options...and in the stress of the moment it's very hard to remember what you planned to do. So think about it now. Think about what you're comfortable with. And talk to the teachers about it. If you want to wait until she's happy (which can take awhile!), you don't need a teacher hovering over you, making comments like "you're just making it harder for her...she'll stop crying once you leave". Or alternatively, if you want to leave, you don't want the teacher telling her that you won't leave until she's ready!

So be ready for the worst. And if it doesn't come, that's great. But don't be surprised if it appears after two weeks of happy drop offs either!