The publishing professionals I know agree that Adobe's InDesign program, for both PC and Mac, is far superior to anything else for desktop publishing. If you're serious about publishing, it's worth the time and expense to get InDesign, and learn it.
As for getting it, that will vary greatly from place to place. If you're ready to start a literacy and reading program, you probably know where to get software. You don't need the latest version; EBay or other places may have inexpensive used software.
InDesign is well-designed, as intuitive as it can be, but that doesn't mean you'll sit down and start using it. Adobe's "Classroom in a Book" series, available in several languages (we have the Thai version) is a thorough and enjoyable way to learn it, and you'll improve your design skills at the same time.
You'll probably want the companion Adobe programs, Photoshop, and possibly Illustrator.
Photoshop is for adjusting and manipulating photographs. It deserves its reknown, but it can be overused. If you've got a young, inexperienced staff, you'll suddenly find that type always has a shadow, and outline, and two other special effects. Pictures will look like they've been through the house of mirrors. You'll frequently need an adult to wag a finger and say, "That's very nice, but we don't always need to use a special effect just because it's there."
Illustrator is for creating and editing "vector" art. That is, art that is made by combining lines and shapes, albeit sometimes quite complicated shapes, rather than by the rows of tiny dots that create a photo. You may not need it. However, clip-art often comes in this format. You can use it in InDesign, but you won't be able to edit it without a program like Illustrator.
And no, Adobe doesn't pay me for saying all this. When a software company makes good programs, issues new versions that are a genuine improvement and not just an attempt to get you to pay again, and creates manuals that you actually want to use – well, they deserve encouragement for bucking the tide.