3 1/2 Year Old Not Talking to Adults

I wouldn't reward him for doing something that may make him uncomfortable. Just keep an eye on it and don't push him too hard. He may be a shy child or he may be overly anxious. Either way, candy won't help!

Does he talk with adults in your home? For many children it is intimidating to interact with big people outside of their comfort zone. I would suggest inviting the teacher to your home for a cup of coffee and see if he is more willing to engage on his own "turf". He isn't really around the teachers that much and he may be the type of child who needs time to feel comfortable.

I would also suggest ignoring the lack of communication. If you draw attention to it, he will become more anxious. If he speaks to an adult, don't over-praise him. Later on, mention to him that you appreciate his willingness to talk to whoever. Don't make a big deal, but let him know that you noticed.

He will probably outgrow this, but stay aware of it! Very unlikely, but it could develop into Elective Mutism, which is pretty difficult to work through. If it doesn't get better, speak with the pediatrician and ask for a referral to a play therapist.

Get him into a public school... Where they will know how to help him out.. Public schools have all kind of helps for kids with problems.. And this is a problem.. Not a severe one.. But one that has to be dealt with. Does he talk to you and your husband.. How about the next door neighbor.. How about grandma... This is good if he talks to all of them.. I wouldn't make a big deal out of it.. Maybe by trying to push him.. It is making him do the opposite..

K., you shouldn't reward your child with candy for anything. Ever.
If your child is shy or has stranger anxiety, a reward isn't going to help him to get over this. Clearly from the experience with husband's family, it takes him a long time to feel comfortable with people. When my son went to preschool at 3, he barely spoke to his teachers, but he did speak to and play with the other children. His 4 year old year in the same school, they couldn't get him to shut up.
Don't offer bribes and rewards, don't try to force him, let him work this out with his teachers.

My 2nd grandson is 5 and he won't talk to most adults because 'they are strangers and we don't talk to strangers'. He's very friendly around those he knows but even the teacher last year at pre school couldn't get much out of him.

Maybe you could try role playing with him. Or talking with him to see if he's just shy or only quiet. No candy bribe for kids.

I have three boys. My oldest is personable. My second was quiet and doesn't mind going into a room, but he likes to check it out first and if it looks okay then he'll go in. My third, is not a people person. It takes a while for him to warm up to people now. He used to cry whenever we take him somewhere but he is doing better but he still doesn't like to "talk" to people. It used to surprised me and made me question why but then I realized, that is who he is. I don't believe in bribing nor offering rewards to talk to people even adults. That may not be who he is. Let him be his own person. Actually, be happy that he's like that because of weirdos out there nowadays. My oldest used to freak me out being so friendly and so outgoing with strangers. Those days are gone now and thank God that he'll be a little safer....