A fast and simple school aged kids knit, short sleeve, slim fitting suitable for over a long sleeved skivvy to keep the core warm, while still able to add another layer over the top
Has buttons in front to make it easy to slip over heads, no sleeves to get wet and mucky while playing.
Worked top down, flat until you form the sleeves, then you join in the round for the body, so no seams, just weave in the bottom end, and use the cast on tail to sew on the buttons
You can add a bit of colour work, or stripes have fun and knit a couple.