Ciao.
成绩:literally it means the results of your exam. However, it has a basic tone of "achievement". Something you will show and more importantly, to submit to someone who is on a higher social rank than you.
结果:result. It could be bad, could be good.
效果:effect. All effects are some kinds of results, but not all results have effects. Failure is an example. Failure is a result, and it can be very quiet. It does not bring any effects unless you can learn something from it.
Add me as friend and we can exchange skype or wechat (better), ask me anyting time if have questions. I will reply you ASAP.
Salute!