Tweenagers

8 to 12 year olds or 7 to 11 year olds.
Found on http://www.cim.co.uk/resources/glossary/home.xhtml?letter=m

tweenagers

young children (ie under 10s) who take on behaviour of older children, eg. having their own mobile phones, 'allowances' and (according to Daily Mail) 'boob tubes, off-the-shoulder numbers and bottom-skimming miniskirts'
Found on http://news.bbc.co.uk/2/hi/uk_news/2614839.stm
No exact match found