I don't get the feeling she's merely "technically underage" from a few things said in the lyrics: Mary is with her peers "in the playground", she isn't interested in "little boys", and the children are being watched by Aqualung "as they play". Those don't describe kids over 14, as far as I know -- and hopefully you don't see fourteen as only "technically" too young for sex! :o)
I don't get the feeling she's merely "technically underage" from a few things said in the lyrics: Mary is with her peers "in the playground", she isn't interested in "little boys", and the children are being watched by Aqualung "as they play". Those don't describe kids over 14, as far as I know -- and hopefully you don't see fourteen as only "technically" too young for sex! :o)