Anyone work professionally with children who are delayed?

I’m a preschool teacher and I have a little boy who will be 5 in July. He’s smaller than the other kids and his mind seems to be that of a 2-3 yr old. All my other kids have progressed and they can spell and write their names, recognize and write letters and numbers, shapes, colors. They can follow directions after I explain what we’re doing on certain worksheets. He can’t do any of that. He only knows his colors. He can’t spell his name by himself. When I hold up his name card and point to the letters he can tell me them then...but it’s a struggle and cannot tell me the U or the L in his first and last name at all. It’s been 7 months in my class and he has not progressed at all. He zones out very often. It’s like there’s a fog in his brain that just stays there. And he knows more about things that he shouldn’t compared to what he should know. Like talking about guns and shooting (his dad is in the military and is currently out the picture as of several months ago) he can point out a Chevy truck by the symbol. But he just seems so lost. And his mother doesn’t seem as concerned as I think she should be. Anyone that’s a professional with this kind of thing...I would Greatly appreciate any help or advice or maybe what you think could be wrong. Thanks.