I am on H-1B - what is the process to switch to student status?

Change of status to F-1: get admitted (about 2 weeks after a complete application), receive the I-20 (about 1 week), then file Form I-539 with USCIS. Regular processing often takes several months; premium processing costs $2,075 extra to USCIS and gets a decision within 30 business days once USCIS has everything it needs. You can generally stay in the US while it's pending, but F-1 study and CPT start only after approval. Nobody can promise the outcome - what we control is a clean, strong file.