Montgomery County Public Schools only goes by the documents he produced when he enrolled and has legally no reason to investigate further --- which I accept. Anybody under 21 can legally enroll in MCPS. Solomon may have shown a birth certificate, which is not so convincing as proof of age.
Even if Solomon is not legally required, to settle this issue of his athletic eligibility once and for all, he should produce the passport he used to travel to Austria, Italy, and the US. If that shows him to be born January 23, 1990, then fine.