Dublinc council website should have a direct contact number to report anti-social behaviour. The street may belong to all but private property I:E the OP's rental isn't something others have the right to use or abuse. It can be classed as criminal damage.

If the council does nothing then film them and report it to the guards, even cite it as a hate crime if needs be, You're French on your own and being targetted when you've asked them to stop.

If yourselves and other neighbors together keep on top of them they'll stop hanging about but on the sly they will kick a ball off the wall or window in passing. Never show fear don't give them a minute to breath.

Your landlord should be made aware as well, there are some legal deterents but the landlord would have to go through legal first, certain height above pavement level clearly marked as a deterrent 'own risk' but theres anti- climbing paint greasy as hell and would wreck their clothes. Might get away with broken glass rendering or spiked trellis and most expensive angled steel palisade railings. Sort of like this face on: vvvvvv, nowhere to bounce the ball off for a clear shot but ugly as hell and highly unlikey your landord would allow it