Gymi to IMS?

My child feels the lack of motivation to continue studying in Kantonschule, and would like to figure out what choices are available. If he would like to go studying in the IMS instead, is it required to attend the entrance exam again or he could just apply for it and then transfer directly?

It seems there's no IMS in Kanton Schwyz, if he goes to IMS Rapperswil at Kanton St. Gallen, I assume the tuition will be quite expensive?

Thanks!