Regarding resign

I joined a school as TGT Science. C.B.S.E private school Maharashtra.1september 2018 and on 15 August 2019 principal called me and asked me to resign or else they will terminate me. When I asked reason he said lots of parents are complaining then I asked which subject then he replied mathametic PRT classes.sir in my appointment latter clearly mentioned that I am appointment as TGT Science then how can I teach mathametic in PRT classes. And actually I already 2 times told Principla please don't give me mathametic in PRT. if you want give me then give me Environment Science bcz it's regarding Science subject and now he forced fully take resign also he said me if you not put resign then I will not give you experience certificate and sir I have that time 1 month newly born baby also so I don't want take risk.so I put resign but in resign I never mentioned any Wear that I am left my job I mentioned there I want to continue my job give me one chance I request This type of line I mentioned there even though they resign me.