Positive:
* Exciting
* Developmental
* Growing
* Transformative
* Independent
* Challenging (in a good way)
* Social
* Discovering
Negative:
* Awkward
* Confusing
* Turbulent
* Pressured
* Insecure
* Cliquey
* Overwhelming
* Stressful
Neutral:
* Transitional
* Intermediate
* Middle-school
* Pubescent
* Formative
* Unpredictable
The best words to use would depend on the context and the specific experience of the individual recalling their junior high years.