I agree with XFSUgimpLB41X. When I did my First Solo in 1986, the average time was 15 hrs. It took me 18 hrs though, thanks to the weather in Toronto during the winter. My flight school's policy was that...if 30 days or more passed between lessons, your next lesson had to be a review of your last one. You couldn't advance to the next exercise. That was BullSh*t if you ask me. It was a way to get more money out of the students. It was also an insult...sugesting that I had no memory! Who knows what Transport Canada's PPL training rules are today.
I remember having a Cessna 150/52 booked for Friday, Saturday and Sunday every weekend for 3 months in the winter of 86, and every lesson was cancelled due to weather! That sure didn't help any.
I guess every country and flight school is different in the area of rules.
Also, some schools allow their students to fly around the pattern 2 or 3 times, performing a few Touch and Go's during their First Solo flight. Some only allow one trip around the patch. Like mine!
PS. I tape recorded my First Solo from the cockpit. It's cool to listen to now and then.