Hi!
Being 17 is NOT a problem to get a M1 student visa.
Check this:
Student Visas
Nonimmigrant Visas | Embassy of the United States London, UK
Excerpt from the US Dept of State website:
Applying for a Student Visa
As part of the visa application process, an interview at the embassy consular section is required for visa applicants from age 14 through 79, with few exceptions. Persons age 13 and younger, and age 80 and older, generally do not require an interview, unless requested by embassy or consulate. The waiting time for an interview appointment for applicants can vary, so early visa application is strongly encouraged. Visa wait times for interview appointments and visa processing time information for each U.S. Embassy or Consulate worldwide is available on our website at Visa Wait Times, and on most embassy websites. Learn how to schedule an appointment for an interview, pay the application processing fee, review embassy specific instructions, and much more by visiting the Embassy or Consulate website where you will apply.
During the visa application process, usually at the interview, an ink-free, digital fingerprint scan will be quickly taken. Some visa applications require further administrative processing, which takes additional time after the visa applicant's interview by a Consular Officer. Also, because each student’s personal and academic situation is different, two students applying for same visa may be asked different questions and be required to submit different additional documents.
Good Luck