If it's going reasonable speed the eye can't track it to contact. That's why movement pitches work.
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allot of times kids will drop there hands when the ball is on the way to the plate, swing under the ball.
You could also try setting the tee on a 5 gallon bucket were the ball is at the top of the chest and hit a bucket of balls. Try to keep your hands alittle above the barrel of the bat on the swing.
In simple terms:
Keep hands in same location across chest as you lower the tee. That means the barrel will drop as the tee is lowered. You can achieve this by tilting (bending) at the waist more, the lower the tee the more you tilt at the waist while keeping the hands going across the chest.
Then go back to the machine.
Straightleg