How to store max y position of object

i have a script for showing height of my rocket but i want to store max height of my rocket to HighScoreText which it reached. this is part of my script ; (sorry for my english thanks for help)

 public class PowerOn : MonoBehaviour {
 
 public Text AltitudeText;
 public Text HighScoreText;
  
     void Update()
         {
     
             float alt = transform.position.y * 10;
             
             AltitudeText.text = "Your Height :" + alt.ToString("#.00") + "m";
     
             if (alt < 1)
             {
                 AltitudeText.text = "Your Height : 0.00 m";
             }
         }

i want to something like your reached max height : 300.00 m this round for example