My school life is a mess Please help?

I got quite good results in my SC exams last year and I got transferred in one of the best schools in the country.I have been able to adapt to my new surroundings and made loads of friends but I can't adapt to the level of difficulties of my subjects. It's been 4 months and my grades are slipping.I am also quite at a disadvantage because all my class mates are taking tuition and not me.I don't know what to do to get back good grades Please help??? [most of the teachers expect students to work out their difficulties by themselves]