Final answer:
Culturing sore throats as soon as possible is the best way to prevent rheumatic fever, as this allows for the timely treatment of streptococcal pharyngitis with antibiotics, which in turn prevents the disease.
Step-by-step explanation:
Prevention of rheumatic fever can best be accomplished by having sore throats cultured as soon as possible. Once streptococcal pharyngitis, caused by Streptococcus pyogenes, is detected, it can be treated with appropriate antibiotics, preventing the development of acute rheumatic fever, which can lead to heart damage if not treated promptly.
The other options, such as keeping children with fever home or sending children with sore throats home from school, are important measures to prevent the spread of infections, but they do not directly prevent rheumatic fever. Treating all colds with antibiotics is not advisable as it can lead to antibiotic resistance and most colds are caused by viruses, not bacteria.