raining cats and dogs: heavy rain; a large rainfall.

rain or shine: an event will go as planned, regardless of the weather.

Don’t worry about the concert getting cancelled. It’s going to happen–rain or shine.

heavy rain

rake over the coals: to be very angry at someone and express that anger verbally.

She raked him over the coals for smoking inside the house.

man smoking

ram something down one’s throat:

read between the lines: to have the ability to read for detail or compehend information beyond what is written.

It’s important to learn how to read between the lines so that you can avoid being tricked into believing someting that isn’t true.

reading

read someone’s mind:

ready, willing, and able: prepared and eager to do something.

He’s ready, willing, and able to defend himself if anyone ever attacks him.

man with sword

reinvent the wheel: to create something that has already been created; to do work that has already been done.

You can easily find lessons online for your students. You don’t have to reinvent the wheel.

wheel
return the favor:
right off the bat:
right on:

right up one’s alley: an area of a person’s expertise; something that a person knows well how to do.

Astronomy is right up Jacob’s alley. That’s why he wants to become an astronomer someday.

alley
rise and shine:

rise to the occassion: to quickly learn how to do something; to adapt.

father taking care of baby
rob Peter to pay Paul: to take money or resources from one and give to another. (This is a biblical reference)
rob someone blind:
rob the cradle: an older person marries or has a romantic relationship with someone much younger. baby
roll up one’s sleeves: rolling up one's sleeves
Rome wasn’t built in a day:
rotten to the core:
rub elbows with someone:
rub someone the wrong way: man driving
ruffle someone’s feathers:
run amok: out of control; chaotic
run around like a chicken with its head cut off:
(a) run for one’s money:
run something into the ground:
running on empty: tired; exhausted; no money
run of the mill: ordinary; average