--- a/net/minecraft/world/entity/animal/AbstractSchoolingFish.java
+++ b/net/minecraft/world/entity/animal/AbstractSchoolingFish.java
@@ -13,8 +_,8 @@
 
 public abstract class AbstractSchoolingFish extends AbstractFish {
     @Nullable
-    private AbstractSchoolingFish leader;
-    private int schoolSize = 1;
+    public AbstractSchoolingFish leader;
+    public int schoolSize = 1;
 
     public AbstractSchoolingFish(EntityType<? extends AbstractSchoolingFish> entityType, Level level) {
         super(entityType, level);
@@ -51,6 +_,7 @@
     }
 
     public void stopFollowing() {
+        if (this.leader == null) return; // Paper - Avoid NPE, plugins can now set the leader and certain fish goals might cause this method to be called
         this.leader.removeFollower();
         this.leader = null;
     }
