Can I convert a tourist visa to a student visa inside Israel?

In most cases, no. The Israeli Population and Immigration Authority generally requires the A/2 student visa to be obtained before you arrive, at an Israeli embassy abroad. Arriving on a B/2 tourist visa and then trying to switch status inside Israel is not a standard procedure and is typically refused. If you are already in Israel on a tourist visa and have been accepted to a program, consult an immigration lawyer urgently — the window for a legal solution may be narrow.