not able to serve notice period due to family circumstances

I am a teacher in a private school , during summer vacations my son was admitted to hospital where he was being operated in emergency .nw he has been advised bed rest ,considering that I need to resign .my employee agreement says I have to serve notice of three months or pay in lieu of . kindly advise is there any way I can resign without serving notice and without paying this hefty amount (my salary is 43000 per month )