It is not clear from your question if you are a High School or a University Student, nonetheless I will give you an answer for both. A) You are a High School Student that wishes to get a Residence Permit within Portugal: A Residence Permit can be issued for high school students, without having to leave Portugal, as long as they have entered legally, which is your case, given that you legally entered with your Schengen tourist visa. B) You are a University Student that wishes to get a Residence Permit within Portugal: A Residence Permit can be issued for University students, without having to leave Portugal, as long as they have entered legally, which is your case, given that you legally entered with your Schengen tourist visa. However, keep in mind that although it is one of the necessary requirements, the letter of acceptance from the educational establishment alone does not fulfil all the necessary requirements for issuing the visa. Other documents are also required, either for the issue of a new visa, thus having to leave the country, or for the issue of a Residence Permit, without leaving the country.
