Is 10 pm a reasonable time for a 13-year old boy to be home for when he is only with his friends in the park - I think this is too late but being a grandparent I maybe behind times.
Ten o'clock is far too late for a 13 yo to be out - IMHO he should be home by 8 pm. You're not behind times at all. We live opposite a park and all year round there are often a group of kids in the park well after dark. I can't see the point really ...
Lots of people are saying in before dark so 10pm is too late - but that depends where you live. It's not dark till after 10 here at the moment. That said, my 14 year old is never allowed out anywhere near that late - 9 at the latest.
My 12 year old has to be home by 7pm and goes to bed at 8.30pm although after starting high school we are going to move bed time a bit later so all the home work can be fitted in!
Way too late to just be "hanging out". If it were someplace like a movie or afriend's house that is different. The parks here close at dusk, so there is always the chance of being arrested for trespassing. (Not that it happens, mind you.) My mother also was not above coming to look for me in her housecoat and slipper. That alone kept me on track and home on time. LOL