oxjess, i must say that i disagree with you a little on your first paragraph.
it all comes down to WHY a child is crying. if a child is afraid and you give too much comfort, they feel like they have a reason to be afraid. they are getting attention for it. it's often best to say, "no need to be afraid" and help them to "brush it off", if you know what i mean. besides, if there are 20 kids in a class, it is impossible for a teacher to be comforting/carrying every child. therefore, it is better to give a little comfort but NOT to make a big deal of it.
as for the second paragraph, all i can say is if you've never been in a classroom with 24 2 year olds, then yes, it can be ok for a teacher to use a raised voice. sometimes it is necessary, just to be heard!
parents/teachers of very young children need 2 voices. voice # 1 is a praising, higher pitch voice that denotes praise and accomplishment. voice #2 is a firm, sometimes louder (depending on the situation) voice that commands authority.
it is absolutely VITAL that BOTH of these voices are used and developed, so that the children can understand when they have done something wrong.
if you've never been in this type of situation, then i'm afraid, it IS difficult for you to understand what a teacher needs to do in order to accomplish some order in the classroom.
and yes, it IS possible to have a group of 2 year olds all sitting nicely and listening. but in order to do this, you first must get them all sitting down.
i find in hk, parent often "reward" the wrong behaviour. rewards should come from the correct/more appropriate behaviour.