Does whether or not boys pee standing up and/or use urinals have anything to do with puberty? When I was in middle school, all boys used the stalls and peed sitting down, but when I entered high school, I found that every boy used the urinals but me.

Many boys learn to pee while sitting and continue to do so as teens and adults even when urinals are an option. It can be a cultural preference or just what is more comfortable for you. There seems to be a shift towards sitting instead of standing for cleanliness (avoiding urine spills on the floor), comfort (urinals may not be the right height for all guys) and privacy; however, either way is fine. According to research, there are no health benefits to standing rather than sitting, unless you have trouble emptying your bladder in which case your health care provider may recommend sitting while you pee.