The filing of the I-526 petition for EB-5 status does not authorize the EB-5 investor to stay in the U.S. To stay in the U.S. and attend school one needs to be issued a student F-1 visa. The F-1 visa is a temporary visa and should be applied for before the filing of the I-526 petition as the F-1 process is a quicker way to obtain a visa for entry into the U.S.
Applying for the student visa first may be the better option. Otherwise, you may run into the problem of dual intent. The EB-5 program is for permanent residency. The F visas are for temporary visits. One of the requirements for the F is to show intent to return to the home country. How can one show that intent with a concurrent process to obtain U.S. permanent residency?