I think both you and your students are right. Successful problem solving is a matter of practice. With an amount of hours per subjects and pre-university knowledge students possess you would probably need more time to teach them how to solve harder problems, but that doesn’t mean they shouldn’t know how to solve them. I can tell you the problems we had weren’t easy. Most of exam problem were from some competition. Also on virtually every theoretical subject I had theoretical part was separated from problem solving part, plus sometimes you would have preliminary qualification quiz(usually 10 question and you had to know at least 6 to pass) which if you failed – hasta la vista until the next exam, meaning that professors wouldn’t even look the theoretical and problem solving parts you did even if they were good enough to pass. On other subjects you needed to have enough point before the final exam and if you don’t you can only try that subject next year by repeating everything from scratch. In any case I think all that was too much.