I have a serious problem please help!! I on a Z type in China for over 6 years

I invited my children over to China last year to visit for 2 months. The embassy granted them 60 days one and they came into China and left after 6 weeks . This year my older son got admission in to Beijing university . So l applied for his student X type and for my second son 13 years old, l applied for an S1 type because l want him to stay in China with me and also go to school here but the embassy granted him an S2 type. I am so confuse. My both children got into China today . Now my problem is how to change an S1 to S2 for him to go to middle school here . Actually my husband is here on a spouse type . I don't want him to go back and stay in my country alone . Please help tell me if it is possible for me to change from my 13 years old S2 to S1 within China .