ت, ث and ٹ all share the same bowl as ب and پ. The dots are everything: ب has one below, پ has three below, ت has two above, ث has three above, ٹ has a small toay (ط-shape) above. Train your child to look at the dots first, not the curve. If they can already tell ت from ث at sight, the script has clicked. Stroke timings are approximate; the discipline is bowl first, then dots above in pairs.

Noticing the difference between ت and ث matters more than writing either one perfectly. The eye that catches the missing dot is the eye that will read fluently. Praise the noticing, not just the drawing.