keep practicing? it would help to know what kind of setup you're on just in case, but it's probably more a question of being more proactive with your board. it takes a while, but at some point you'll figure out how to use that "wood plank" to your advantage. it shouldn't feel like you're dragging a 2x4 along with you, but more like having a diving board attached to your feet. just keep doing those presses and ollies (and of course the penguin walk) and eventually you'll start feeling lighter on your board.
and ignore those kids that make it look easy. it is NOT easy, especially not at the beginning.