She really was the school "boff" and won school prizes, etc, which she may not have done at grammar school. When she had completed her GCSEs, the grades were so good that she got a place at the local grammar to do her A levels, which she is doing now.
The message is that your child can still do well, you just need to encourage him/her and carry on the good work into their teenage years, which I am sure you will do.
Totally agree. Self-confidence is the most important in one's life. I am now worrying about this, though my child just got top level scores in a grammar.