I've used the Oliver + S School Bus Tee to make a 3/4 sleeve gathered skirt dress, an A-line dress with front pocket, and a basic cardigan. The School Bus Tee is my go-to kid's t-shirt pattern, but there are plenty of others to choose from. I like this one because the sizing is always spot on, for my kids.
1. For the cardigan I cut a few inches off of the length of the front, back, and sleeves, then added knit ribbed cuffs to the waist and wrists. I cut the front piece in half along the fold line, and added a button band to each cut edge.
2. For the gathered skirt dress I shortened the body of the t-shirt to just under the arm opening. I shortened the sleeve by a few inches to make them ¾ length. The skirt is two rectangles joined at the side seams, gathered at the top, and sewn to the bottom of the t-shirt bodice.
3. The a-line dress is the short sleeve t-shirt made longer, and wider at the bottom hem. The kangaroo pocket is drafted based on the size of my daughter’s hands.