Yes, we have lost sight of the weight we should be. At this age, children can look 'in proportion', and they tend to overgrow 'in proportion', so being over-high is as bad as being over weight, in terms of long term outcomes with obesity. So, at five, you may think your child is right for their height, but only 1 in 10 children are naturally that big, so unless both parents are also tall, it's unlikely yours is that 1 in 10.
www.ncbi.nlm.nih.gov/pmc/articles/PMC1713231/
This is something I have worried about, having a 91st centile height child, but last time he was weighed, his weight was 50th centile, and his height being 91st centile fits his predicted adult height, so I think we're okay. But should we get a letter, despite swimming, gymnastics, a healthy diet, and other sports, I wouldn't go to the paper and practice my 'sad face', I would be taking it seriously, and taking action, even though my child 'looks all right', because we just can't tell these days. We've screwed up our views on body image, terribly.