My child is in my custody, but my former husband says he makes the school decisions. Who is right?

Both have a role: hadhanah is day-to-day care, guardianship is authority over the child's person and property. Act 303 s.88(1) says that although the right of hadhanah may lie with someone else, the father is the first and primary natural guardian of the person and property of his minor child. But s.87(1) says a custody order, subject to any conditions imposed, entitles the person given custody to decide questions of the child's upbringing and education. So the answer depends on what your court order says. Reread its conditions, and talk it through for the child's sake. The Quran describes the nursing of a child after separation being decided “by mutual consent and consultation between the two” (Surah al-Baqarah 2:233). See Hadhanah & lineage.