In adults, a penis that measures 3.67 inches or less when gently stretched is a micropenis. Micropenis can occur on its own, but it often accompanies other health problems due to hormonal disorders or congenital (present at birth) conditions. Your child's symptoms will depend on the cause of the micropenis.
That's an interesting topic. If stretched means that you only tear a little on the flaccid penis, mine is 2.75 inches and would be in the range of a micropenis. But fully erect it measures 5.12 inches which is not much but nevertheless in the normal range. As a teenager I was a little embarrassed to notice that most of my classmates (we were only males) had longer ones in the flaccid state. But nobody made fun of me and for this reason it was not a big deal.
Perhaps you may know Earnest Hemingways biographic novel "A Moveable Feast" in which he describes his life in Paris. In one chapter he mentions F. Scott Fitzgerald, who felt inadequate as a man because his wife Zelda critisized his small penis. Fitzgerald asked Hemingway about this and he answered "'Come out to the office".
But read the story for yourself:
https://thebestamericanpoetry.typepad.com/the_best_american_poetry/2009/03/hemingway-reassures-fitzgerald-about-his-penis.html
It's quite possible that Hemingway's description is fictional since Fitzgerald at that time was more successful as a writer and Hemingway could be jealous of his success.
Back to the locker rooms: During school I never had any problems in the locker rooms since my breast was flat. My gynecomastia (I stay to call it this way since it does not disturb or trouble me, it's just a word) arose after an age of 45 years. Within five years, at 50, I had a C cup. As a longtime wearer of compression stockings and compression pantyhose the ladies at my orthopedic supplier recommended a bra with the words "you wear pantyhose which is called a female item, so why not wear a bra to support your breasts?" This was a valid argument.
I was an avid sauna visitor until the year 2005. The sauna at the town I lived at that time had a locker room for both sexes! All the time you noticed women unhook their bras and put off their panties and males putting off their underwear (or vice versa). I did not wear a bra at that time but if I had I surely would be embarrassed only because of the males in the locker room and not of the females.
As I wrote in one of my comments some time before I stopped wearing bras since I like to let swing my 40 C breasts freely. There are so many women - even with larger cups - who stopped wearing bras that I tried the same and like it too.