@sim Kids are dumb and kids who think they aren't dumb are the dumbest of all. That makes them very easy to take advantage of.
Personally I think a tiered system would be ideal. Before you're 18 or 16 or whatever, current age + something rather small like 2-4 years would be fine. A 15 year old dating a 17 year old probably isn't an issue, but a 15 year old dating a 20 year old probably is, and a 15 year old dating a 30 year old definitely is. The tricky part is picking the exact numbers.
Yeah, I like that tiered system. It's a good rule of thumb in general once puberty happens and the interest in other people begins. Those can happen at different times.