Series of fiction books on teenagers wrote either in the 1980's 0r early 1990's?

I think of Sweet Valley.Series of fiction books on teenagers wrote either in the 1980's 0r early 1990's?
Three series spring to mind immediately:





The Tom Swift books written between 1910 and 1941 by Victor Appleton


The Hardy Boys books written between 1927 and 1979 by Franklin W. Dixon


The Nancy Drew books written in the 1930s by Carolyn Keene





All of those were created and produced by Edward Stratemeyer and are generally similar.





EDIT: Oh I read those dates wrong, oops. I thought you said late 1890s early 1900s. Wow..... Sorry that's what I get for answering questions at 4am.Series of fiction books on teenagers wrote either in the 1980's 0r early 1990's?
The Animorphs series is what I think of.
Twilight yay!





GO TEAM EDWRD!