Hello, I appreciate your concern for your student. The medicines Ritalin and Focalin help the ADHD and Oppositional Defiant Disorder patients by changing amount of some of the chemicals in brain. They need to be taken regularly and continuously to achieve the desired results. Starting the medicines suddenly, stopping abruptly or taking them once in a while when symptoms go out of control may not work and it may also carry risk of severe adverse effects with the potential of not having any effects on these medicines in future. I would advise you to make your student s mother understand these facts and ask her to get her son on regular medications. A mental health professional can help to make the mother understand the facts. I hope this information helps. Thank you for choosing HealthcareMagic. Keep up the good work! Best, Dr. Viraj Shah