Who sings the theme song to welcome back kotter?

Written by John Sebastian.

Welcome back, your dreams were your ticket out.

Welcome back to that same old place that you laughed about.

Well the names have all changed since you hung around,

But those dreams have remained and they're turned around.

Who'd have thought they'd lead ya (Who'd have thought they'd lead ya)

Back here where we need ya (Here where we need ya)

Yeah we tease him a lot cause we've got him on the spot,

Welcome back, welcome back, welcome back, welcome back.