Both are grammatically correct, depending on their contexts

If you want to find out whether people actually write that way, you can google "what I learned is" and find examples.

所有跟帖： 

• 學到的東西是過去學到的所以用learned，但過去學到的東西現在還在還適用所以用is -abookl- ♀ (0 bytes) () 10/29/2015 postreply 05:54:06