"Heinlein juveniles" are the novels written by Robert A. Heinlein aimed for what would now be known as the "young adult" market. The core group are the 12 Heinlein novels published by Scribner's between 1947 and 1958. A 13th, Starship Troopers, was submitted to Scribner's but rejected and instead published by Putnam. A 14th novel, Podkayne of Mars, is often listed as a "Heinlein juvenile", although Heinlein himself did not consider it to be one.
The intended readership was teenage boys, but the books have been enjoyed by a wide range of readers. Heinlein had great respect for the children who read the books and was eager to present challenging material to them, such as the firearms for teenagers in Red Planet. This led to "annual quarrels over what was suitable for juvenile reading" with Scribner's editors. In addition to the novels, Heinlein wrote two short stories about Scouting for boys and three short stories with Puddin', a teenage female protagonist, for girls.
Read more about Heinlein Juveniles: The Scribner's Juveniles, Starship Troopers, Scouting Stories For Boys, Puddin' Stories For Girls, Podkayne of Mars, Ties To Other Works