diff --git a/stanza/utils/datasets/ner/convert_he_iahlt.py b/stanza/utils/datasets/ner/convert_he_iahlt.py
index 81b40aaba..b1550b1da 100644
--- a/stanza/utils/datasets/ner/convert_he_iahlt.py
+++ b/stanza/utils/datasets/ner/convert_he_iahlt.py
@@ -6,73 +6,93 @@
 import stanza.utils.default_paths as default_paths
 from stanza.utils.datasets.ner.utils import write_dataset
 
+_RE_ENTITY_SPLIT = re.compile(r"([()])")
+
 def output_entities(sentence):
+    # Build a single print call for all entities in the sentence for faster output
+    entities = []
     for word in sentence.words:
         misc = word.misc
         if misc is None:
             continue
-
-        pieces = misc.split("|")
-        for piece in pieces:
+        # Avoid repeated split if there's only one piece
+        if "Entity=" not in misc:
+            continue
+        for piece in misc.split("|"):
             if piece.startswith("Entity="):
-                entity = piece.split("=", maxsplit=1)[1]
-                print("  " + entity)
+                # Use partition for more efficient single split
+                _, _, entity = piece.partition("=")
+                entities.append("  " + entity)
                 break
+    if entities:
+        print("\n".join(entities))
 
 def extract_single_sentence(sentence):
     current_entity = []
     words = []
+    append_word = words.append  # Localize method for speed
+
     for word in sentence.words:
         text = word.text
         misc = word.misc
-        if misc is None:
-            pieces = []
-        else:
-            pieces = misc.split("|")
+        pieces = misc.split("|") if misc else []
 
         closes = []
         first_entity = False
+
+        # Fast path for common case of no entities
         for piece in pieces:
-            if piece.startswith("Entity="):
-                entity = piece.split("=", maxsplit=1)[1]
-                entity_pieces = re.split(r"([()])", entity)
-                entity_pieces = [x for x in entity_pieces if x]   # remove blanks from re.split
-                entity_idx = 0
-                while entity_idx < len(entity_pieces):
-                    if entity_pieces[entity_idx] == '(':
-                        assert len(entity_pieces) > entity_idx + 1, "Opening an unspecified entity"
-                        if len(current_entity) == 0:
-                            first_entity = True
-                        current_entity.append(entity_pieces[entity_idx + 1])
-                        entity_idx += 2
-                    elif entity_pieces[entity_idx] == ')':
-                        assert entity_idx != 0, "Closing an unspecified entity"
-                        closes.append(entity_pieces[entity_idx-1])
-                        entity_idx += 1
-                    else:
-                        # the entities themselves get added or removed via the ()
-                        entity_idx += 1
-
-        if len(current_entity) == 0:
-            entity = 'O'
+            # Use the faster in-string check to avoid startswith unless needed
+            if not piece or piece[0] != 'E' or not piece.startswith("Entity="):
+                continue
+            # Use partition rather than split for a slight speed gain
+            _, _, entity = piece.partition("=")
+            # Avoid repeated regex compilation with the precompiled one
+            entity_pieces = [x for x in _RE_ENTITY_SPLIT.split(entity) if x]   # remove blanks
+            entity_idx = 0
+            entity_pieces_len = len(entity_pieces)
+            while entity_idx < entity_pieces_len:
+                piece_value = entity_pieces[entity_idx]
+                if piece_value == '(':
+                    # Combine assertion into conditional for a very modest gain
+                    if entity_idx + 1 >= entity_pieces_len:
+                        raise AssertionError("Opening an unspecified entity")
+                    if not current_entity:
+                        first_entity = True
+                    current_entity.append(entity_pieces[entity_idx + 1])
+                    entity_idx += 2
+                elif piece_value == ')':
+                    if entity_idx == 0:
+                        raise AssertionError("Closing an unspecified entity")
+                    closes.append(entity_pieces[entity_idx - 1])
+                    entity_idx += 1
+                else:
+                    entity_idx += 1
+
+        # Avoid unnecessary list operation if current_entity is empty
+        if not current_entity:
+            entity_tag = 'O'
         else:
-            entity = current_entity[0]
-            entity = "B-" + entity if first_entity else "I-" + entity
-        words.append((text, entity))
+            entity_tag = current_entity[0]
+            entity_tag = "B-" + entity_tag if first_entity else "I-" + entity_tag
+        append_word((text, entity_tag))
 
-        assert len(current_entity) >= len(closes), "Too many closes for the current open entities"
+        if len(current_entity) < len(closes):
+            raise AssertionError("Too many closes for the current open entities")
         for close_entity in closes:
-            # TODO: check the close is closing the right thing
-            assert close_entity == current_entity[-1], "Closed the wrong entity: %s vs %s" % (close_entity, current_entity[-1])
-            current_entity = current_entity[:-1]
+            last = current_entity[-1]
+            if close_entity != last:
+                raise AssertionError("Closed the wrong entity: %s vs %s" % (close_entity, last))
+            current_entity.pop()
     return words
 
 def extract_sentences(doc):
     sentences = []
+    append_sentence = sentences.append  # Localize append for small speedup
     for sentence in doc.sentences:
         try:
             words = extract_single_sentence(sentence)
-            sentences.append(words)
+            append_sentence(words)
         except AssertionError as e:
             print("Skipping sentence %s  ... %s" % (sentence.sent_id, str(e)))
             output_entities(sentence)