Mercy College based in NY but has an online degree or certification only in teaching literacy (secondary).
These programs are not specific to 7-12, but I would look at what might be done through these among others: Central Michigan University MA in Reading and Literacy K-12 Eastern New Mexico University MA in Pedagogy and Learning Concentration in Reading and Literacy Michigan State University MA in Education online Concentration in Literacy Education Western New Mexico University MAT in Reading
Saint Joseph University in Philadelphia offers a Reading Specialist Certification for K-12. Maybe you might want to try that out !