A Level Swing Isn't Swinging the Bat Level with the Ground

There is a lot of controversy concerning the angle of the bat when hitting a pitched ball. Based on watching film of great hitters and what has proved successful for the kids I work with (and in line with Ted Williams' approach to hitting), a level swing is not swinging the bat level with the ground. A level swing also only refers to the path of the bat head through the hitting zone, not the initial part of the swing involving the hands coming down to the ball or the follow through after contact.
A level swing involves swinging the bat level with the path of the pitch. This is a slightly upward swing (the degree to which depends on the pitcher). This increases the likelihood of hitting the ball squarely, even if contact is a little too late or too early. When hitting down on the ball (which is popular among many coaches), the hardest hit balls will be grounders. Lines drives will flutter and only occur when slightly undercutting the ball. Weak line drives are also produced by big uppercuts and the only hard hit balls will be high fly balls (which are easier to catch than low fly balls).
Correcting for uppercuts and undercuts begins with the position of the hands when the stride foot is planted (launch position). Aside from the hands being over the rear foot at this point, their height is also important. Uppercutting (more than what is required by the path of the pitch) often occurs because the hands start too low and often by the ribs. Undercutters generally start their hands too high, somewhere above their shoulder. Ideally, the hands should be close to shoulder height. From the rear shoulder, the hands should bring the bat head down into the hitting zone and then up at the ball. When the bat head flies forward, it should go through the contact area level with the path of the ball.