using my weekends and vocations 有误,应改为 on weekends and in my vacations（注意,vocation 是职业,vacation 才是假期）
during ...kept teaching 虽然也是“一直在教”的意思,但用在这里不是很恰当,应改为 for ...have been teaching,
全句：For the last three years,I've been teaching junior middle school students English on weekends and in my vacations.