Mesh included, however I do recommend that you visit Cocomama's post
here as she has also made other wonderful mesh conversions for teen guys.
Here are 16 plain shirt re-colours of Cocomama's open shirt with jeans for teen guys mesh.
They are organised into 4 sets with 4 outfits in each set.
Set 1.

Set 2.

Set 3.

Set 4.

Credits:
Mesh - Cocomama