In the big leagues, a left-handed reliever is sometimes brought into the game to neutralize a left-handed batter. Lefty hitters tend to do well against right-handed pitching. Think of great lefty hitters like Babe Ruth, Ted Williams and Ichiro. In youth leagues, there usually aren't many left-handed hitters on the opposing team - maybe one or two. Sometimes they are good hitters, but a lot of times they aren't. Once in a while, there is a switch hitter on a team, but they tend to have a regular side they hit from during a game. Switching pitchers, or pitching arms, between batters at this level isn't necessary and can dissrupt the rythm of a young pitcher. So I suggest alternating right-handed and left-handed pitching by inning. Start with the weaker arm, then switch to the stronger arm the following inning. During a game, my son would usually start out pitching left-handed , then pitched the next inning right-handed after warming up in the bullpen during his team's tur...
Learn about ambidextrous pitchers – from Little League to the MLB.