Possible Version 1
It’s three weeks since you fell ill. I guess you have suffered a lot in the hospital, but are you feeling any better now? We’re concerned about your health. And we all miss you very much.
In the past three weeks, we've been buried in study because the exam is around the corner. But don’t worry about your lessons, with which all of us will help you when you are back. Besides the routine work, we held a football match in our grade and our class won the championship. If only you had been with us!
We hope you will soon recover and join us in our colorful school life.
Possible Version 2
It has been three weeks since you went to hospital. How are you feeling now? Hope you will recover soon because all of our classmates miss you very much.
As you may know, we have just finished our mid-term exam. I am very happy to say that I made great progress this time. I really appreciate your encouragement. Besides, our school’s sports meeting will be held next Friday and Saturday. Our class did really well last year and I believe we would get more prizes this year if you were to join us.
We are looking forward to your coming back.
Take care of yourself!