what's the structure of a sentence

No. As usual, this sentence has been done many things to, and needs to be unwound.

There's one main clause, in skeleton form

• The issue was debated

and also a subordinate gerund clause that's the object of an adverbial preposition with

• (with) children coming to our schools speaking more than 200 languages

which itself contains yet another adverbial gerund clause, this time with A-Equi

• (children) speaking more than 200 languages

OK. Now, back to the main clause, which is a Passive clause, via Conjunction Reduction from

• Indef debated the issue hotly at the grass roots level and
  Indef still debates the issue hotly at the grass roots level

So the structure of the sentence is what's visible on the surface. Just like the structure of an iceberg.