Should Players Play Club & High School at the same time?

For many states, this practice is already prohibited or limited, often times citing player safety centering on a concern that coaches would not coordinate workouts and risk the health of the athlete due to overtraining. 

For those states that do allow it, my answer is "it depends" on the perspective you want to view it from and more primarily the goals of the athlete. The injury perspective is valid -especially in girls where they are 7x more likely to have knee injuries in these ages than boys.

From a growth and development standpoint, these are two very different environments (in theory). Club should be on a long term development model where high school should be on a short term competitive model. The daily decisions are quite different, especially in terms of comfort zones. Club should have you routinely out of your comfort zone to maximize your rate of learning, whereas high school should primarily place you in your comfort zone to have the fastest most confident version of yourself at the table. These are competing objectives directing the daily decisions differently in both environments. The skill sets are complimentary and players do need both, but the blend ratios depend on the recipe you're cooking.

I do say in theory, because there are multiple coaches in each who try to run their program like the other...HS as long term developmental and club as short term competitive. Neither are really set up to do that successfully but some are convinced to try.

You then have to look at the students in the classroom. One is a narrow bandwidth skill and concept wise as well as shared objectives. The other is (typically) a much wider range of skill and concept control as well as shared objective. This simply means both are not equal in their potential as a learning environment, and they are also different as a competitive environment.

I say all this as background for the most basic question that is often overlooked: what is the goal of the athlete? Most will have goals that allow for participation in both because the objective is not that scarce. For them, go ahead.

For those chasing more scarce objectives, go to the environment that adds the most to your future competitiveness and not the other. In theory this should be club but it is not always. As I said earlier, there are multiple coaches misplaced in both. The coach should be in the other environment based upon their objectives but for whatever reason aren't.

There are so many permutations to the answer that I've seen over the years that I think it is incorrect to assume a formulaic answer like club this, high school that.

The main distinction for me is if the goal is not scarce, then do both. If the goal is scarce, do not do both. Do the 1 and fill time with higher level pickup games (peer coaching) against older better players.