Make sure you type
/localinfo -u and then try. Try sending to several different people to make sure it's you with the problem and not the person you're sending to.
The most likely reason however, is that your school does have some sort of block on DCC (it's prolly aimed more at the ports needed rather than the mIRC feature!) so try talking to the tech dept. Please be aware we don't help with evading school policy etc
Also make sure that you read over
this thread.
G'luck!
Regards,
