P.S. Kindergarten was only a half day and the purpose was to prepare them for first grade. Nowadays we rush them along and I am not sure it is wise. Are we robbing them of the necessary dependency of their infancy?
He is not even three years old. Many children of that age are not ready to be separated from their homes. I would take him out of school and try again next year. We forget that it is only recently that such young kiddies are sent off to school. Time was that six-year-olds started school in the first grade. Some children went to kindergarten at age five. And that was it!
You mention his lunch box. Is he staying a full day? I'd see if you could arrange shorter hours, and not every day of the week or even close to that.
The anxiety he's displaying would make me think twice about sending him at all, until he is a little older. But you might be able to get him to relax about it a bit if you could do something like a couple of half-days a week.
As special mentioned, your presence in the classroom might calm him. If volunteering is not possible, is it possible for you or your mother to sit in, for a few days, not to interact with him but just to be there so he can see everything is fine with the place (by your reaction)? I know the teachers often tell the moms just to leave, but that is usually to keep the mom from hovering over the child. If you were just in the back of the room, sitting there and smiling and looking calm, he might glance at you for a cue but keep doing what he is doing. It would be up to the preschool, whether to allow this.
Social anxiety is a big deal, I would treat it seriously at this point so it does not become ingrained. If he can't stop crying, I would respect this and wouldn't go the "tough love" route that some of your friends are probably recommending.
Hm. Well, first-------- he is very young. Hopefully he is being eased into this with only one day a week or something like that. Too much too soon may overwhelm him.
Second, I'm so sorry he is so uncomfortable there. I think that I'd make an effort to socialize with him more with kids his own age. Play dates are what needs to happen. Whoever takes him and picks him up needs to get friendly with other parents of the kids and ask someone to meet at a park, or invite them over or whatever to help him along with his social skills. Then you or your spouse or mother actually stay involved in the play date to help him with the other kids. At home, play with him like he is a peer. He must share his toys with you, he must sometimes let you go first, he must let you pick a game to play, etc. so that he gets used to the idea of some of the things you do with other kids. At 2.9, kids are still doing parrelel play meaning they play beside another child but still by themselves. But his discomfort level is a bit concerning.
Do you think he is having social anxiety? There are things you can do to make this better starting with the increased socialization with you present. I'd try to volunteer or have your mother volunteer in the class. I'd always remain positive about school.
And reality is that some kids simply are not emotionally ready for school at this young age. If this turns out to be the case, withdraw him and try again next year. It won't kill him to go a bit later. School is fun but you can't convince him of that as it is not fun now. I have a good friend that had a child who cried every day of preschool for a month. Finally, she withdrew him. This same boy went back the next year, a year older and loved it.
good luck