The answer you may be looking for is without a doctor's release (ringworm treated by over the counter medicine) typically a kid should not practice and expose others until the signs of ringworm are gone. If you read the websites (I only look at webmd as it has some credibility and fact-checking) the earliest should be 48 hours after treatment has began. The real answer appears to be that every case is different and as long as the fungi is present, it can be spread. It doesn't even have to be person to person. It can be left on the mat, on a dirty towel, jock, underwear, etc. Fungus lives longer in moisture and if you keep using the dirty towel it can reoccur. My advice is to immediately get a kid off the mat, send them home from practice or the tournament, and quietly advise the parents to see a doctor and get the fungus treated. Do not allow them back into practice until a doctor clears them from ringworm. Also continue to check them as some kids have had reoccurrences as it wasn't completely gone. Clean your mats every night and use protective foam. Go to www.defensesoap.com and they have great teatree soap that many athletes use and the protective foam and matcleaner. Look at your wrestlers on Monday or Tuesday and if they still have their weight and age brackets on their arm, talk to their parents about bathing practices. Impetigo and ringworm are nasty problems and hygiene, prevention, and treatment are of the utmost importance. Hillbilly takes a bath every day... good luck to you.