Its junior.... my son is 5,2 aprox.... should i buy a junior??
If your son really has an interest in camping and being outdoors, then I would recommend going with down not synthetic. My son's interest in being outdoors has grown, and with the money I've spent buying synthetics at just the right size to get him buy (I bought 3 synthetics over the years), he could have been using a space-saving, comfortable, light, down bag.
Personally, I buy quality product and expect to use it for the long haul. I use a bag that is 15+ years old right now. With that in mind, this LaFuma Junior bag is good up to 5'4". Unless your son is fully grown at 5'2", I'd go with a standard adult bag good up to 5'10-6' or so. Your son will then be able to use that bag well into adulthood. The caveat would be if there is a younger sibling who will grow into this Junior bag in 1-2yrs when the son in question grows out of it. In this case, it may be the way to go. Hope that helped.
Have fun outside,