My dd was actually almost-4 when she started, her birthday fell right after the cutoff, so she was 3 for the first week of class, and then 4.
Whiel she didn't cry or make a scene, it definitely did affect her. She became even MORE attached, but in a "bad" way. Very clingy, she lost all the positive independence she had prior, she literally won't be in a different room from me anymore. I have a now-5 year old shadow, lol. She started being very rebellious, angry at me, sad. not at all the happy, adventurous person she had been. Like i said, she never cried or whatever, but EVERY day she asked, no BEGGED, not to go to school. We tried to figure it out, but she never had anything concrete or fixable to say about it...she just didn't like school and didn't want to go. She wanted to stay at home with me and brother. I went and observed..she SEEMED fine during the day, her teacher loved her, said she was a great student. DD defnintely learned stuff, there wasn't an issue there.
We pushed through, thinknig it would get better...but it never did. We finished out that year, and went back this year. It was okay the first week or so, she was sort of happy..and then the begging began again. She "hates" school, she doesn't want to go, she wants to stay home.
We finally made the decision to remove her. She is now homeschooling.
I think Montessori philosophy is great. I think academically, kids tend to learn a LOT from the method. I thini the classroom environment is good, I like the emphasis on the individual child and respect, etc. Out of all the institutional schooling methods, it's my fave.
She just didn't want to go. She complained, said she hated all the works, and wanted to stay home. *shrug*
I think my dd is pretty atypical, lol. But we tried for over a year, and gave up. We are not of the mindset that kids "have" to go to school. Homeschooling was always on the table for us. Like I said, we loved a lot about the Montessori method and thuoght dd as going to blossom and grow at her school. But, she hated it. So....it's over. I'm a little sad, becaues *I* like being a part of something, a community. But I had to honor my dd's needs.