Both can have impact. It doesn't have to be "or".

Consider the horrors of summer vacation. Never again.

They closed them then re-opened them in time for one of the biggest waves of asylum/undocumented immigration in recent history, part of which incentivized bringing children (who often need ESL and cultural integration assistance) who then are entitled to attend public schools whether or not the school has been allocated the resources for such influx. Such re-allocation of finite resources to include so many students with extra integrative needs would track well with across the board drops regardless of race.

I can't imagine what it is like to be teaching 29 or 30 students and one pops in after crossing the Darien Gap, possibly witnessing people being raped and swept away by the jungle, then having to go on and go straight into learning arithmetic -- and then realize this is happening at mass scale. "What is 5 - 1?" The number of us remaining after we crossed the last stream.

Visa based immigration pathways, especially the non family linked ones, tend to display this effect less prominently since professional visas bring in people who on average paying higher property and other taxes and have had the resources to prepare their children for school in the US.