"Toho" is the genitive form of "ten" (the, that), and also the accusative form for masculine animate nouns. It is "(tam)toho" in this sentence, because "that boy" is the direct object of the verb, and so in the accusative case.
"To" (the, that, and sometimes this) is both nominative and accusative for neuter nouns. You would use "(tam)to" if, for example, the object in this sentence were "auto" instead of "hoch."
Not sure I've quite answered your question, but maybe there's something useful in there!