Unless you're failing I wouldn't drop it. All my LC Science teachers as in BIO,CHEM and PHYS said that you don't even need to do science for JC to do higher for LC but obviously it will be harder. The ordinary level exam has pretty similar questions only that they will tell you exactly what to do while with the higher level paper you need to think for yourself and practise doing papers a lot
What level are you doing now? How badly are you doing in the exams? If its less than 30% then Ord Level is for you. Otherwise you need to practice lots and lots of exam questions. Try to complete 15 mins revision 2 or 3 times a week to help improve your grades.
Ord Level for JC does not automatically put you in Ord Level for LC but you would be at a disadvantage when compared to others who did H Level for JC