There are some physical syndromes, such as Morquio syndrome, that manifest as small stature. Has his doctor said anything about testing to see if this is going on? I'm surprised his doctor is not interested in his height not being as big as average.
Oh I am sorry he gets picked on , if he is eating well and is strong , he may have a growth spurt and gain height and weight, what does his doctor say about it ? meantime how about he does more in the way of sports to up lift his self esteem , is he ready for some judo or mind building jitso I think at this stage building that self esteem will help a lot, get him excelling, then size wont matter .If he gets bullied you may want to ask the teachers to watch what is happening ,Good Luck
Also, he was born on his due date at 5lbs 14 oz. He eats ALL THE TIME. He isnt picky, either. But he was furious to find out that he should still be in a carseat instead of a booster seat because he is under 40 lbs. Children over 4 are supposed to be in a booster (because normall they are over 40lbs.) People pick on him constantly because he is so little.
He is well below the 3rd % for weight and height on the growth charts. Generally, though, because he is small for weight AND height, it's likely that his BMI (body mass index) is within normal limits. Doctors tend to look to bmi rather than one measurement of either growth or height. If he was a tall kid with low weight, they'd look a little closer.
Some kids are just small, and he started out small. A lot of things when it comes to growth are dependent on factors such as whether his parents are small, where he started out on the growth charts, how his growth has charted over time. More of a concern would be whether or not he has crossed percentiles, but in my opinion, any child not on the growth charts deserves to have a work up done if one has not already been done. There are a variety of non-invasive tests that can be done to rule some things out. It can take some time because once it is brought to the attention of his pediatrician, they will likely want to plot him over time, but a good pediatrician should be doing this on a regular basis anyway.
If has no other issues, I wouldn't be too concerned, but it definitely warrants a look to put your mind at ease. There is something known as constitutional growth delay, which is a naturally occurring delay in growth that is familial in nature. In other words, he may end up having his growth spurt later in life than others, particularly if his father did.
I understand your concern about him being teased about his size. My daughter has already encountered this at the tender age of 4. Other children wanting to treat her like a little doll and pick her up. It hurts her feelings, but I can imagine this is particularly more difficult for a little boy.
Someone has to be the smallest in the class. That's what people tell me. But it's no comfort when you have a 27lb 4 year old....or a 33lb 6 year old. Also, there are car seats you can buy that have more of a big boy booster seat feel, but that still have the five point harness....the brand escapes me at the moment.
I think you should request that his doctor take a closer look, but do it in a way that assures your little man that he is just fine. That good things come in small packages. Good luck!!