All peoples did this and will do this...
That's where you're wrong. A lot of people do not meet the requirements, and a lot of people simply don't have enough qualifications. So more and more young people will end up living on benefits, simply because they can't make a start anywhere. When you flood a country with foreign workers, it doesn't take a genius to figure out that someone of the indigenous population who just left high school won't be able to find a job to finance a study, or anything else for that matter, unless you're lucky enough to have successful parents who can help you a hand. Oh, and of course there will also be foreign workers who won't be able to find a job in an already overcrowded country, which means they're going to apply for benefits aswell, or remain in the illegal circuit.
How do you think the mighty USofA got populated???
Well, if someone allowed me to work a simple job in my own country, then maybe I could actually buy a ticket to try my luck elsewhere.