Sun/Cloud visual behaviour charts are woefully outdated now. They've generally been frowned upon for at least the last 10 years now and rightly so. It means that one blip can cloud the whole day (pardon the pun). We deal with behaviour in the moment. An incident is dealt with, the child is given the opportunity to put it right and then we all move on. One bad choice does not need to make for a bad day where they remain on a cloud for all to see.
I disagree with those saying "it doesn't publicly shame them as children are all aware of who is misbehaving anyway". In a Reception classroom, where most of the children are naturally still egocentric, it's totally normal for children to miss misdemeanors of others, as they're so busy focusing on themselves. A Reception classroom is a very busy room with lots going on. Some children may be aware of an incident involving someone else (especially if they themselves are involved in some way), but over the other side of the room they're probably oblivious and rightly so. The misdemeanor doesn't need to be advertised by a child's name visibly moving down. This draws everyone's attention and gets them all talking about who has moved down, asking the child in question what they've done etc. They may have never known if there wasn't a visual chart. Therefore it does indeed publicly shame by drawing unnecessary attention to children who may have made one wrong choice. It's usually the same children that move down every day, so they don't learn from it. All it does it let the other children know that they been 'naughty' again (in their minds). That sh*t sticks.
These systems also cause unnecessary stress to sone children who are usually very well behaved, depending on their personality. Some really fear the pressure to remain on the sun (or move up to a rainbow, if there is one. Not moving up can feel like a failure to some). Without a chart, if the teacher needs to have a quiet word with a usually well behaved child it's unlikely to ruin their day, as most of the class will know nothing about it and they can quickly move on after putting it right. Whereas moving down on a chart feels like the end of the world to those children. Everyone knows what has happened. It is shaming.
I would actively avoid any school running this type of system, as it's not inclusive. It also suggests the school aren't up to date with latest wellbeing thinking and advice. I wouldn't want my child going to a school which is stuck in it's ways, as this is very outdated thinking. You can have high expectations of behaviour without ranking each child in terms of how well they meet those expectations.
Star of the week is different. Most schools will do this, and it's a way of rewarding children for doing something exceptional for them. It's very much differentiated and personalised to children's own abilities and personalities. Every child can and should get it at some point, but that doesn't mean it's just a meaningless token well done for everyone. Every child deserves to feel special and have their moment, whatever it's for. Any school who don't ensure everyone gets it at least once are again not being inclusive. Every child will do something to earn it at some point, if you look hard enough for the positives. It shouldn't always be about who listens the best, or produces the best work, or is a kind friend etc. There are all sorts of things children can be awarded star of the week for. Shame on those teachers who don't seek the positives in everyone.