2000004505

Out of $15$ boys and $15$ girls in a class, $5$ boys and $5$ girls got A, $5$ boys and $5$ girls got B, and another $5$ boys and $5$ girls got C on a Math-test. (There were no Ds and Fs on this test.) Determine the smallest value of $n\in \mathbb{N}$, so that if a team of $n$ children is set-up, then certainly at least two children of the same gender and with the same grade are on the team.