Can you do this with a 300mW laser pointer? (10 points)?

So i've ordered a 300mW laser pen and i was wondering if it would engrave things because me and my friend are 14 and we've just moved into a new school building and we're Y10 and we liked the idea of writing our names in permanent marker on a wall so people would remember us and we could possibly go back to that school in years to come and see it (you may think it's stupid but we like the idea) we then realized it would just be painted over, so we came up with the idea of engraving our names into a wall with a very strong 300mW high powered lazer (green) so will it work? You may think it's a stupid idea but please, humour us. (10 points best).