Age out while on AOS

[Sanjoy Purohit]

Hi, 

I have question for my son, his I-485 petition was filed in July-2007 and is still pending (along with mine) as my priority date still not current (PD:Jan-07). Our approval may take longer than expected due to huge backlog for Indians. I heard after 21, (will turn on Oct-16) he may not be eligible to receive green card under my petition. I don't really understand CSPA policy. I request guidance on this topic and would like to know if this is true? 

Also, what options are available for him in to continue staying in US and pursuing his college study?