When your birthday happens to be on a school day this year, you will need to deal with certain issues regarding your party. Some schools do not allow birthdays to be celebrated there so you will need to have your party either at home or at another venue after school. Okay. Let's say you have decided to have your b'day blast at home after school. Other problems should be looked into like after-school activities in which classmates and other friends could be involved in. So you need to consider the time after school----maybe late in the afternoon? If this is going to be the case, other friends may not be able to make it because they need to study for the following day's homework or they'd be too tired to go so your party will not be as fun-filled as expected.
There are many hitches and glitches in giving a birthday party on a school day. Are you willing to postpone it to a weekend so everybody can go? If yes, then maybe that should be considered.