If you can hit, they will find a spot for you. Tee work, soft toss, wiffle ball games for fun, batting cages. In the winter, tee work into a tarp and I got a bag of popcorn and would throw soft toss in the basement with the kernels. Kids loved to peg me with them. Made a mess but the focus required to hit them was intense. plyo balls. Hitting for average on any high school team is key. You need power to get past high school.
There was one batting coach in town that threw a ton of balls and made up tons of silly games to make them focus on achieving something. Had to hit the L-screen, back of the cage 8 out of 10. Get a "hit" 4 out of 5. Can't hit the floor or pop up, etc... Miss the goal you get 10 push ups.
Insane focus on the basics.
You can throw them a ton of grounders to get repetition. 10 to the middle, 10 to left and 10 to the backhand. 10-15 minutes and your done. Inside or outside as long as you have about 12' of space. YouTube coach Washington from the Braves. Start on knees then move up. If it's good enough for the pros... Hitting grounders takes too much skill for most dad's or mom's, anybody can roll one. Maybe use a warped ball for difficulty.
Outfield. Have them stand in the middle and throw it around the clock and make them react. Run football routes and make them catch the ball on the run.
Joe Madden's saying "do routine better."
Initially, you can start these drills and try to make them fun. Eventually, they have to start dragging you out to get better.