I have come across literally thousands of immigrants who have come here legally and are very productive citizens. I especially favor people who are educated in medicine, finance, science & engineering. Knowing what these educations cost in US, it is a free gift to our country when they arrive. If you examine post graduate students in any major university in United States you will be amazed at the percentage of students from foreign lands. These spots could have been filled with American born students, but for some reason they are not. Obviously many Americans do not aspire to study hard and advance to the highest level of knowledge to be gained in post-graduate college.
So we need all the brain power we can get. We will not be a great country without people with highly developed skills.
George Mason University in Fairfax County Virginia gets caught doing that with some regularity.