Capitalization, schmapitalization. As trivial as it may seem to your first grader, remembering to write the proper letter—whether it be lower or uppercase—is one of the most important skills for early writers to learn. This worksheet ingrains it in his memory by getting him to practice putting an uppercase letter at the beginning of each sentence and at the start of each proper noun.
Try out the other worksheets in this series for more help getting into grammar.