As an immigrant and a parent myself, I think you meant to say "children of illegal aliens". US _legal_ immigration is means/skill based and requires a paying job, so kids of immigrants mostly are fine economically.
Illegal migration is a big problem, but I'd also counter that this problem should be mostly confined to the Southern states and CA.
No, I meant legal immigrants — for example, my son's school has a fair number of children from Central America and Ethiopia and, unsurprisingly, their math scores fare better than their English.
Legal immigration is a substantial majority of the total (roughly three quarters):
High-skill immigrants are certainly a great economic contribution but they're far from a majority with less than 20% percent having a Bachelor's degree:
… and even if they were, that doesn't mean that they and their families have high English fluency. Unless they happen to have grown up in a bilingual household or attended a bilingual school, their children are almost certainly going to have to catch up to their peers before they'll be able to understand their teachers and read the coursework no matter how skilled their parents are.
Illegal migration is a big problem, but I'd also counter that this problem should be mostly confined to the Southern states and CA.