Dear laura:
Hi!I'm Sam.I am a Grade ×（你自己的年级）Class××（你的班级） student in ××（你的学校）now.I am do well in English ,Maths and Chinese.My teachers think I am a good student now .We learn Art,Music,Computer and the other activities
as well.We often do some after-school activities.I think it is very interesting to do .But we have more homework than your school,so I don't have enough time to sleep.I often spend ×（你做作业的时间）hours doing homework.And after doing homework,I usually reading books.On Saturdays and Sundays,I often visit my grandparents'.Sometimes,I listen to pop(popular) musicand play computer games.I'm interested in playing computer games,but my mother always thinks it is not good for my eyesigeht(视力.也可写为eyes）well.
I hope you can write letter soon.(结尾,你自己看情况而定.老师应该给你们过结尾吧）
Yours penfriend sam