It (be)_____ not until he feels too tired that he goes to bed.
is
It is not until his father is angry that he (tell) _____ the truth.
tells
It was not until we (begin) _____ secondary school that we studied English.
began
It (be) _____ not until midnight that she went to bed.
was
It was not until yesterday that the letter (deliver) _______.
was delivered
It was not until he was 18 that he (start) ______ using a cell phone.
started