You can not have Lightroom for free for more than 30 days.
You can avail the Student discount. Please check the below link for more information about the pricing.
Wow, that is an amazingly misleading web page.
The Photography plan for students and teachers is $9.99 per month, which is not (as it is claimed on that web page) "save at least 60%", it is in fact saving $0.00 (which is 0%) compared to the price non-students and non-teachers pay.
In other words, if you just want Lightroom, there is no student discount. (If you want the entire Creative Cloud, there is a student discount)