The chances will depend on the availability of vacancies. Schools can only accept transfers of students if they have met the school’s cut-off point of the posting year.  You may like to refer to MOE website for more information 

(https://www.moe.gov.sg/microsites/psle-fsbb/posting-to-secondary-school/faqs.html).

To appeal, please submit your application via https://form.gov.sg/5f96453b2464570011d2fee5