DS7 reduced the cuffs of his school sweaters to rags last year and has spent the summer mutilating his t-shirts - cuffs and necks. He tells me his teeth sometimes bother him and that it helps him concentrate in school (I suspect the latter might just be him telling me what he thinks I want to hear!). I've been debating the pencil chewies and necklaces - which he actually says he'd wear and use - against waiting it out. It's probably a cheaper option than repeat visits to the uniform shop! He's used a screw cap water bottle for years without spills or lost caps (or chewing it!), so I'd highly recommend that option. Now I'm going to google chewie bling...
