hight performance

forgive my poor English, but i really want to have my problem fixed and join you though i am not a programer.

i use drupal6.6 to convert my origin website , which is a great flux one in my school about 5000IP/day .
i fixed a lot of problems through GOOGLE , tpl.php,form.api,CCK+VIEWS,etc

but i really come up a problem : too slow to do some update after login!

every day , my website will have 50 students and teachers have to update their information like news and so on . they tell me that the new test website(drupal) is great but the performance is too bad.