Correct. Strictly speaking, so long as the girl is a willing
partner 16 years of age and above, no laws can be considered to be
broken.
That said though, the teacher had performed a massive breach in the
expected professional conduct of teachers. Regardless of whether or
not the girl was a willing partner, a clear line should always be
drawn between teachers and their students.
Teachers should be educators and mentors to their students, and
nothing else.
I call for the removal of this fella from the teaching profession
effective immediately.