We've had great success with Levi's. We do run into the length problem sometimes though.

Agreed. Old Navy is great for this, and I love Target's adjustable waist jeans.

Same problem in our house. Levi's skinny jeans fit him in the leg, but the waist is ridiculously big. You might try H&M. We've had some luck there.

This is a big problem - the obesity wave in the US means most places (especially cheap ones) don't carry anything to fit a skinny 12-14 year old boy. No Levi's fit our son. I called customer service, they said we should "feed him more". The UK Levi's site has jeans that fit but it's too expensive.
We gave up and bought some boots for him instead to offset the high-water look....

Levi's makes some very slim fit jeans.

Yep, Old Navy is great for slim sizes.

We have this problem. Lands End slim cut and Old Navy work best, but I have still had to had those taken in at the tailor. I only do it for one or two pairs (my son prefers the "athletic" style pants which usually have a drawstring, which helps this issue), so it is not too expensive.

Target carries slim sizes with elastic in the waist for additional adjustment.

Lands end slim fit. Sears carries them.

Have you tried Old Navy, Kohls, or JC Penney? I know a lot of people on DCUM wouldn't dare set foot in some of these stores (!), but they all used to have slim jeans that my tall, skinny boy could wear.

It is impossible to find jeans for our tall and skinny 12-year-old. Either they are ankle-length, or the length is fine but you can put two of him in there. Can you suggest a place where we might find something suitable?