Being at practices each week is important to growing as a lacrosse player. But on the off days, there are important skills you can work on at home to accelerate your development. As previously mentioned, working on cradling and scooping are key to a player's growth. Another skill a player can work on at home is passing & catching with wall ball.
Find a brick wall (probably without nearby windows) and pick a spot on that wall. Players should aim to hit that spot repeatedly while catching it. 15 minutes a day will help players improve their passing and catching skills dramatically. For more variations, check out this video.