Whitening school polo shirts that have embroidery

[Mackemh]

Hello,
I've just been looking at my daughter's school polo shirts, from last school year, and noticed that they're no longer "white" white. I'm not sure how to whiten them, as they have the school logo embroidered on them, and a blue border on the collar.

Can they be whitened?

I've already looked at replacing them, but there's none in stock for my daughter's size (and the shirts can only be brought from one local shop).

Thanks

I wash whites separately, but I also do a wash of 'semi-whites' which include white polo shirts with black edging - 60deg+, bio washing powder and soda crystals. I add Napisan sometimes too.

Thanks Cynderella - do the soda crystals help whiten? I've never used then before.

Have you tried leaving them outside in the sun? According to another thread on here, that bleaches out even tomato stains.