12 year old dating
I'd focus on curfew, I'd limit activities for a 13 year old to 9pm, but might let a 17 yr old stay out until 11 or 12, depending on the individual.
I am a mother of two kids one is 13 and another is 11.
But my personal opinion is that if they want to go to a movie or other activity together, and a parent will drop them off and pick them up from that activity, I think 13 or 14 is perfectly Ok.
Make sure to act interested but not too interested in your teen's dating life with the hope that they will open up to you if they run into difficulties. Friends are marginally ok but not romance of any sort. If they don't experiment, they won't know how a relationship works in the real world.
They may have more trouble expressing their feelings. I believe that kids should be able to start "dating" at ages 13 or 14, if they want to.
....woman who wrote the letter needs to stop thinking in terms of "late" bloomers especially when she mentioned her husband and dating. There are plenty of people who didn't date until they were in their late twenties or thirties.
There is nothing wrong with wanting to not make your parents upset and nothing wrong with focusing on school either.