Dinky Hocker Shoots Smack! by M.E. Kerr, 1972

A story of Tucker Woolfe, Dinky (Susan) Hocker, Natalia Line, and P. John Knight. Young love, teen angst, inattentive parents, ends with Dinky spray-painting "Dinky Hocker Shoots Smack!" all over sidewalks, buildings, cars in the neighborhood when her mother is being awarded the Good Samaritan award for her volunteer work with rehabilitated drug addicts.