(un)helpful information

Is it better to be pre-warned about people or to get a rude shock when they do something? I am completely divided. The intentions of the warner probably have a lot to with the answer, if they merely want to help you not run into trouble regarding another individual there is a possibility it can be useful and not destructive. However if it is to merely colour your opinion of somebody they don't like for whatever reason, or to simply cause difficulty, the obvious answer is NO.

Pre-warnings come in the forms of 1. helpful advice from new acquaintances (at a new school or workplace, somebody usually gives you the rundown of everybodies revolting lives and intimate details of their various sins)
2. Pass on notes between teachers about children they have taught to give the new teacher a heads up.
I imagine there are others but these are the main ones.

I would like to suggest that both of these are negative and rarely help. Unless somebody is in danger from an individual there is no need to warn them about anything purely because you did not get along. I have found that such information given on others tends to colour my opinion of them however hard I try not to let it. Now if the information is positive, this is fine, how nice, kind, funny, loving, generous, thoughtful, helpful, Godly or whatever somebody is, that is uplifting for both the subject of discussion and the discussers. Anything negative though must be classed as slander and gossip UNLESS, out of love, you are warning somebody of the dangers of associating with an individual because of things they have done.

Children can pass through from Kindy to high-school without anyone giving them a chance to prove themselves because each teacher warns the next about the trouble maker. What if it is just that the first teacher they had clashed for whatever reason and otherwise they were fine.

I would much rather make my own opinions of both adukts and children based on my observations, uplifting words about ANYONE are welcome as they may help me to see the good bits of people I struggle with. Negative words are just destructive and unhelpful, I don't want to hear them.  Bearing in mind I am guilty of this on occasion.