I found this pill in a child’s backpack, have no clue what is is. White round on one side it says ATLOL 50 on the other side nothing.
Not to play Google Queen or anything, but could it be this:
I can’t find any picture that matches that
CairoCarol and I agree. Most likely Atenolol, 50mg. A very common, inexpensive blood pressure medication basically (lowers BP). Relatively unusual for a younger person to be prescribed it. Very easy for a child to have obtained one out of their parent’s or grandparent’s supply. Even mistakenly, thinking it was a more exciting medication, like Ritalin or Xanax, which is what it looks it at first glance. Or could be black marketed as those two (drugs of great popular choice for abuse) by an enterprising young capitalist.
You may not be finding the exact picture match because it is a generic version, but just as marketable. Or there could be a perfectly innocent reason for it being in a backpack, like it was found rolling around on the floor.
Whatever the reason, do not let a child take it, dangerously low blood pressure could ensue. Fainting, falling etc., safely dispose of it-i.e. ask your pharmacy to dispose of it, should be free. Don’t flush it or trash it. Not good for environment or water supply.
Keep a Drugs.com app handy. Lets you look up anything by shape, color, imprint.
See, all those years of nursing school put to good use. 
Ok thanks that’s probably what it is, I appreciate it.
During my time in law enforcement, whenever I came across an unknown pill, I would call Northern New England Poison Control at 1-800-222-1222 and describe the pill. 98% of the time, they were very helpful identifying it over the phone.
And yes, I have caught kids crushing and snorting their grandparent’s blood pressure pills… 
I take 50mg of Atenelol and I just looked…mine says ATN 50.
But, when I read the OP I had the same thought as the rest of you…
When traveling by air, as a family, we often designate our kid’s backpack to carry small light things that we may need access while flying. Things like iPads, breath mints etc. This is because we don’t keep the kid’s backpack in the overhead compartment but with us under the seat in front of us.
Although, I don’t keep my medications there, I can see if a parent put the drug in the backpack pocket and then either didn’t find it or forgot about it.
Just another possibility to consider.
When I was in high school, someone was selling pills scavenged from a relative which were heart or blood pressure meds of some type. The seller told everyone to just take 1, because if you took 2, you’d be really affected - so of course, numerous kids took 2. So 8 students fainted in class that day and were taken to the nurse’s office. Fortunately, nothing worse happened.
Related topic, but not completely, in that my kid has a well-known prescription. He uses Guanfacine, which is another lo-tech (old) medicine for treating high blood pressure, but it has the side effect of helping him to control himself.
(He’s on the autistic spectrum, high-functioning, but in the past he needed the Guanfacine more than he does now. We prefer the use of this drug, with its very light calming effect, to something psychoactive, which could mess up his brain.)
Does everyone realize that we’ve given pool a lot of information with none given in return… I want some human-interest story!
Was it your child? Did you ask what it was and where they got it? Did they not know?
Or did you want to know for sure what it was before you had The Big Drug Confrontation?
I for one am hoping there was a simple explanation, and that you and the kid got to talk openly about it.