can I change my L visa to permanent residence?

Yudo, it's impossible to change the L type into a permanent residence. I think what you meant to get is the temporary residence permit, right? You can change the L type to S1 type at the local exit and entry adminsitration by submitting all required documents, as your passport, application form, bare-headed photo, your wife's passport and residence permit, an invitation letter from her and the invitation letter from the school. Then apply for your residence permit after the S1 type is issued.