At the moment, all you can do is file Form I-130 for your son to get him in line for an immigrant visa as the son of a lawful permanent resident. You may do this so long as he is unmarried (if he marries he has to wait until you are a citizen before he can immigrate through you). There is a waiting list for these visas, but it has gone down quite a bit in the last few months, and I believe is now under a year. Once the I-130 is approved and a visa becomes available to him, he file the papers to apply for his green card.
Ideally you would want to file the I-130 petition as soon as possible so there is a chance that a visa will become available to him before he turns 21. After he turns 21, he goes into a different visa category where the wait times are much longer. But you should also know that, if you file an I-130 for him, it will jeopardize his chances of being able to renew his student visa. This is because, to get a student visa, you have to show non-immigrant intent and being the beneficiary of a petition for an immigrant visa is not consistent with non-immigrant intent.
In short, there's a lot more to consider here than just what forms you need to fill out. There are some difficult strategic choices you will have to make about when to file. In addition, you have to make sure you make a good presentation when you apply to remove the conditions on your residency so you don't put your green card, and by extension your ability to petition for your son, at risk. Because of this, I recommend discussing your son's options in detail with a qualified immigration attorney.
Scott D. Pollock & Associates, P.C.
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Chicago, IL 60602
(312) 444-1950 (fax)
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