The whole thing is a bit sketchy. I often wondered myself as my son's travel team gathered at a baseball facility on Sunday nights during the winter and we saw a rival school's freshman baseball coach (wearing the school's baseball hat, to boot) working with 30 or so kids. Us coaches kind of went "Hmmmm."
The IHSA's Section 2-School By-Laws (specifically, Section 2.09) gives an illustrative example (#69) of a school conducting pre-season conditioning with the answer of "no". Specifically,
69) Q. May a school conduct pre-season conditioning for a team prior to the starting date for any sport as outlined in Section 5.000 of the IHSA By-laws?
A. No. Conducting a preseason conditioning program as outlined above would constitute a violation of IHSA By-law
2.090. (By-law 2.090)
However, Section 3-Athletic Eligibility By-Laws (specifically, Section 3.16) describes "Open Gym Limitations." I suppose off-season workouts, conditioning, etc., without coaching instruction, could qualify under the parameters of "open gym."
Section 5-Sport Season By-Laws describes the time frames for the sport seasons, natch. Section 5.01 relates to fall baseball.
Here are the links to applicable IHSA by-laws:
Section 2-School By-Laws - See Section 2.09-Season Limitation in Athletic Activities
http://www.ihsa.org/org/policy/2008-09/section2.pdfSection 3-Athletic Eligibility By-Laws - See Section 3.16-Open Gym Limitations
http://www.ihsa.org/org/policy/2008-09/section3.pdfSection 5-Sport Season By-Laws - See Section 5.01-Boys Fall Baseball
http://www.ihsa.org/org/policy/2008-09/section5.pdfIf you want any of the other sections, you can type any of the links into your browser and change the section number. Enjoy!