Being a multi sport athlete is great, being a one sport top athlete is great too. Schools will recruit the kids with the best athletics and top grades , so if playing multi sports is draining time away from studying, maybe specializing is better because there tends to be some relaxed time during down seasons, where multi sport athletes usually have to be training hard each season. Remember- the grades will get you the best scholarships. Each kid is different and you should direct them to do what makes them happy, well rounded and what will help them get where they want to go for their long term future.