IMO both are required. I'm lucky in that I did a lot of plain SQL early on, and found ORMs later, but I think ORMs do cut out a lot of time for quick-and-dirty queries that end up not being the bottleneck. The problem arises once you find a bottleneck, you won't know how to optimize it if you haven't done a bit of SQL mucking about earlier.

Also, the big thing is you won't know how to translate to other ORMs if you don't know SQL. Eg once you know that you want an index, it's a matter of a web search to find out what the syntax is in your ORM. But if you just started with ORM, you might not realize that kind of thing is part of how it works.