I believe the system should be overhauled somewhat.
Under 14 any sex, consensual or otherwise should be treated as sexual assault for the sake of the children involved. This is not a provision to go after the 13 year olds, but simply to allow their family life and history to be examined carefully as sex at 13 or under is very often an indicator for sexual abuse in the past.
From 14-18 the current Romeo and Juliet laws are excellent, and two consenting people should be allowed sex. The age gap here is up for debate but I believe within 2 years should work well. This serves to protect highschool freshman from upperclassmen while still allowing relationships.
The reason I place the general age of consent at 18 is that it is serving as the age in which someone can engage in sexual acts with someone of any age. The current system allows for relationships between mature adults and highschool sophomores, which is something I view as unhealthy and I think is a common opinion.
This system places a greater weight on the mental well being of those involved than societal values, I happily admit this as I believe that should be the focus of these laws. To protect children while still allowing for exploration and growth in a safer environment. Couple this with healthy sex ed in either the 8th or 9th grade which focuses on respecting sex as a meaningful act and on protection from pregnancy and STDs and the result should be healthier more mature young adults.