Few questions about Tier 4 student visa

Hello,

Hoping someone can help me with a question in regards to UK Tier 4 Student Visas. I would appreciate it.

Can a non-EEA citizen, studying an English language course with a private provider in the UK, extend their Tier 4 visa for longer than the course duration on the CAS if they wish to study further?

ie. Student enrols on an English Language course for 1 year. At the end of the 1 year, the student wishes to study another year.

The course is a 'full time' course at 15 hours per week at a Tier 4 private sponsor. Private sponsor in this case meaning an private English teaching school (ie. not a college or university).

Many thanks