The same treatment (weeks 21-28) will be repeated for a total of 6 times (until week 68). After week 68, all patients will receive daily 6MP and weekly MTX with pulses of dexamethasone and vincristine every 4 weeks until week 100, after which only 6MP and methotrexate will be given. Intrathecal treatment will be given every 8 weeks only to patients at high risk of CNS relapse after week 48 and will be discontinued after week 96. Continuation therapy will be discontinued after 120 weeks in girls and after 146 weeks in boys