As I'm teaching Pascal to two guys 12 and 10 years old, I'll tell you that certain abstract concepts don't go well below certain ages. Search on google about it, plenty of sources to read. Scratch is a good option for elementary school and all the programming concepts from the bare basics all the way to the complex stuff. Object Pascal might be better suited to 14+ yo, depending on the proficiency of your alumni. Mine are smart and I'm not teaching them anything they can't chew and swallow.
And remember that Pascal was designed for teaching programming, and good programming behaviours, so it might be too strict for elementaries who would rather make an airplane sprite move around than to learn what is a record or a *gasp* pointer.