.

Break into the school, Mission Impossible style, or break into the house the same way, your pick.

Panic!

Call your friend and ask permission to break in, beware of his neighbors?!

make a giveaway?

btw what is the key's connection to your friends cats?

Remind me to never let you watch my cats.

You clearly need to enter self-induced exile. You've failed your friend and the cats, your honour is broken. Enter the great salt planes and never return.

Just call 911 http://www.youtube.com/watch?feature=player_detailpage&v=2cXDgFwE13g#t=85s

Get ready to buy some new cats and a 'I'm sorry' card.

kill yourself

facility manager of the school? cant be that hard to get in an public building...

pick the lock, take the cat back to your house

You could always try to pick the lock xD

Open the lock with two hairpins on youtube you'll find a video guide!

Just go to the school and ask the administrator/guards to let you because you have the key in the locker.They will let you in.If they don't go to the director, he should be there.

Try breaking into the house and get arrested.

Call the Humane Society in Canada or the SPCA if in the USA. They may be able to facilitate your situation.

Search online for the custodian of the school (janitor) and contact them.

Contact friend see if they have emergency hidden keys or relatives have a set of keys.

Contact Landlord/Superintendent if friend rents.

Let's hope things work out and start praying before you try the above things.
Optimism and faith work wonders.

You'll need this and this

throw food into the chimney, the cat will find it!

Don't panic!/By Douglas Adams/ Contact one of your teacher! He/she will be help you out!

rent a deli slicer and put tiny slivers of meat under the door for the cat

break into the school

search for one rock near his front door thats faker than the others

take this quick and easy "lockpicking in 48 hrs" class online, the cats won't starve in 48hrs clicky:

buy skyrim or x game and give it to your friend

Why were you supposed to watch over your friends cats? Where is your friend? Can you call him and ask if there is a second key that you can get from a family member or another friend?

Also do you have any superpowers?

Break into your school, get your keys, and pee all over the place.