This post was written at least a year ago... but I figured I should post it anyway. It still applies. This was inspired by "growth strips" sewn into petticoats and dresses in from what I am guessing to be around the late 1800's to early 1900's. (I guess, but I did not look it up, feel free to correct me if you'd like). Think Laura Ingalls Wilder in Little House on the Prairie or discontinued Victorian era Samantha (American Girl) doll's petticoats, just merged with modern jeans.
School will be starting again soon, and thus the mad rush to clothe your children for the school year. I sort of hate shopping, so I want to get it all over with as much as possible. Which means buying jeans that are too long for my children. I've resorted in the past to simply rolling the hems up (since I knew they'd grow into it halfway through the year, if the knees held out until then). But I thought of this and had to try it out instead. It is actually deceptively simple.
Put co-ordinating thread in your machine and a heavy duty needle. Measure from the bottom about 2" and fold (and pin). Sew 1/2" away from the fold. Repeat for as many tucks as you need. Each tuck shortens the jeans by 1 inch. Super simple! Then when it needs to be let down, you just unpick them starting from the top.