Conjurations in general are left out of apprentice books, with the exception of tanglevine in the beastmaster book. I'm not sure the exact reason, but it could be because of the lack of space in the limited arena size for apprentice games, or to reduce the complexity of learning spell types and rules some what. Either way, I don't think a channeling strategy would fair well in apprentice. Those games are short and brutal. They only get drug out by the players inexperience. Other than learning the spells and strategies, plus a general nervousness to engage, the whole thing is set up for a butt-kicking session that does not reward building up or control.
