A 10% ESL student population doesn't solve itself. That's like a child thinking that their refrigerator magically fills itself when it gets empty. If you ignore that solutions have costs than yes by your definition ESL students have no costs associated with them.
I asked about the strain on the legal system due to immigrant populations, specifically the prison system in California. You said we should put less people in jail. While that's true it doesn't solve the problem unless we're going to change our laws to the extent that aggravated assault is no longer a crime. Then we've once again solved the problem by refusing to admit it even exists.