Hey,

The difficulty of any paper is completely upto the capability of the student. Some students find physics and maths tough while some find it difficult to learn the processes involved in the biology.

So you need to see what your interests are. From my perspective I find Maths and physics tough whereas biology and chemistry was damn easy for me.

So, the correct order of increasing difficulty would be, BIOLOGY, CHEMISTRY, PHYSICS, MATHEMATICS.

Hope that helps.

Thank you