I would be a bit careful about beginning Read to Someone and choosing partners when considering the lowest readers. Perhaps you "rig" a game, where the kids have to find perfect partners. I've done this with a bit older kids, but think you could make it work for 2nd. Begin by thinking of either people, characters or things that are thought of in pairs. Examples might be Jack and Annie (Magic Tree House), Ivy and Bean, Tom and Jerry, Mickey and Minnie, bread and butter, peanut butter and jelly, for examples. You'd have to pick ones that you think your kids would know pretty easily. Write each of the partners on a card, mix up (see the next statement). The "rigging" part comes when you think ahead about who would be good partners for those strugglers, pull the cards for the matching partners and let those kids choose first. You have to be a bit savvy, but it can be done :).
When deciding which kids would be good partners for your strugglers, think about this: Rank your students high to low as readers. Divide the list in half. Start with the "middle" to partner up with the lowest readers (of course considering personalities, as well). Have the pair start with books the lower reader is successful with; usually the middle readers are fine listening to lower books, and they feel like the strong reader, but can let the lower reader be successful.
Does that make sense?
