At least you were lucky that the mother only called the principal and the principal called you and none of them decided to call CPS just in case. 😄

As you are not sick yet it's probably fine. I assume the seafood was cooked and the salad marinated including something acidic like lemon juice and/or vinegar? This helps preserve the seafood as opposed to the pieces being exposed to air by themselves. Of course this is no recommendation to eat months old salad just because it's marinated but it is an explanation for it not tasting horribly yet.