ACS Junior's PSLE results crashed in recent years. Their grades are like your regular neighbourhood schools because they have a huge local alumni whose kids are not well-verse in Chinese like your new citizens from PRC and Malaysia.
The new PSLE AL scores penalize student exponentially for their weaker subject and they cannot use better grades in English, Maths and Science to average up their weak Chinese.
In the end, most ACS primary's kids cannot make it into elite secondary schools through PSLE. They either LL enjoy the affiliation advantage to their ACS secondary or parents scramble to pay $30000-50000 to "coaches" to get into better schools via DSA.