Hello thanks for asking from HCM Marijuana is cannabis and it is a common substance of abuse in youngsters. Smoking marijuana is known to cause amotivational syndrome. The syndrome is characterised by lack of desire, poor motivation, chronically apathetic mood. As the symptoms are persistent and are causing significant blow to your school performance I would advise you to visit a psychiatrist along with your parents. Stimulant medicines like amphetamines, adderall can result in improvement of symptoms like increased motivation. But these drugs are known drugs of abuse and as per my opinion these drugs will not be of much benefit in your case because of liability of abuse. Other drugs like Modafinil are also good option. Modafinil improve day time alertness and increases drive and motivation. The drug is non-addicting and you can consult your psychiatrist for that drug. Low dose of anti-depressant medicines will also help in poor motivation. Try relaxation exercises, yoga, meditation for better mood. Running and exercise result in release of endorphins which help to improve mood. Hope this helps you, thanks