I made a school jumper 3 years ago for child#1 and it’s still in use for child #2. It was made with Debbie Bliss Cashmerino and washes quite well. It has frayed somewhat at the sleeves though.
I have learned the hard way why our ancestors worked their clothing bottom-up. If a garment frays at the hems, where it is most likely to, then the damage runs further and faster when the garment is made top-down, than if it’s made bottom-up.
I picked up stitches below the frayed area. I picked up a further 2 sts either side as well.
Then I worked in the original pattern (baby cable rib) for the same length as the cuff. I picked up a St from the jumper at the corresponding point at the start of each row. I cast off by working slip st into the cuff cast-off and slipping the previous St over. The cuff cast-off was quite firm actually, as I had replaced that recently.
Unfortunately, I don’t have any marching yarn and I had to guess at the needle size (3mm?), so this is a very visible mending. I’m quite determined that this jumper will last for as long as it fits. There may be more patching ahead!
Honestly though, I think I have to just bite the bullet and get another ball of baby Cashmerino and rework the cuffs.